diff --git a/application/editormodetrack.cpp b/application/editormodetrack.cpp
index 0b264b78..5b048396 100644
--- a/application/editormodetrack.cpp
+++ b/application/editormodetrack.cpp
@@ -1159,7 +1159,35 @@ void editor_mode::render_path_parameters(TTrack &Track)
 		finish_edit(rebuild::none);
 		ImGui::InputFloat(STR_C("Sound distance"), &track->fSoundDistance, 0.0f, 0.0f, "%.1f");
 		item_tooltip("Distance between the rail joints in metres, sets the rhythm of the wheel clatter; -1: the default");
-		finish_edit(rebuild::none);
+		finish_edit(rebuild::parameters);
+		if ((track->eType == tt_Normal || track->eType == tt_Switch) && (track->iCategoryFlag & 15) == 1)
+		{
+			if (ImGui::InputFloat(STR_C("Unevenness (mm)"), &track->m_uneven, 0.0f, 0.0f, "%.1f"))
+				track->m_uneven = std::clamp(track->m_uneven, 0.f, track_uneven::most);
+			item_tooltip("Peak deviation of a rail on a 10 m chord. Id-14 limits: 6 mm at 160 km/h, 10 at 120, 18 at 80, 35 at 40.\nWith a sound distance set, the rails also dip at the joints. Joined switches use the lowest of their values");
+			finish_edit(rebuild::parameters);
+			struct component
+			{
+				char const *label;
+				float *value;
+			};
+			for (auto const &part : {component{"Up and down (mm)", &track->m_unevenup}, component{"Sideways (mm)", &track->m_unevenside}, component{"Cross level (mm)", &track->m_unevencross}})
+			{
+				if (part.value == &track->m_unevencross && track->eType != tt_Normal)
+					continue;
+				if (ImGui::InputFloat(STR_C(part.label), part.value, 0.0f, 0.0f, "%.1f"))
+					*part.value = *part.value < 0.f ? -1.f : std::min(*part.value, track_uneven::most);
+				item_tooltip("Set apart from the unevenness, mm. Negative: the unevenness");
+				finish_edit(rebuild::parameters);
+			}
+		}
+		if (track->eType == tt_Normal && (track->iCategoryFlag & 15) == 1)
+		{
+			if (ImGui::InputFloat(STR_C("Dip at rail joints (mm)"), &track->m_jointdip, 0.0f, 0.0f, "%.1f"))
+				track->m_jointdip = track->m_jointdip < 0.f ? -1.f : std::min(track->m_jointdip, track_uneven::most);
+			item_tooltip("Depth of the dip at each rail joint, every sound distance. Works with unevenness at 0. Negative: 0.4 of the unevenness");
+			finish_edit(rebuild::parameters);
+		}
 		ImGui::InputInt(STR_C("Quality"), &track->iQualityFlag, 0);
 		item_tooltip("Quality of the track, 20 is the nominal one; lower values give a rougher ride");
 		finish_edit(rebuild::none);
diff --git a/editor/editorTrack.cpp b/editor/editorTrack.cpp
index 418d908f..cbe7c26b 100644
--- a/editor/editorTrack.cpp
+++ b/editor/editorTrack.cpp
@@ -152,6 +152,11 @@ editor_track::state editor_track::capture(TTrack const &Track)
 	for (auto const *isolated : Track.Isolated)
 		result.isolated.push_back(isolated->asName);
 	result.overhead = Track.fOverhead;
+	result.uneven = Track.m_uneven;
+	result.unevenup = Track.m_unevenup;
+	result.unevenside = Track.m_unevenside;
+	result.unevencross = Track.m_unevencross;
+	result.jointdip = Track.m_jointdip;
 	result.sleepers = Track.m_sleeper_enabled;
 	result.sleeper_frequency = Track.m_sleeper_frequency;
 	result.sleeper_model = Track.m_sleeper_model_name;
@@ -250,6 +255,11 @@ void editor_track::apply(TTrack &Track, state const &State)
 	Track.fTexSlope = State.texslope;
 	isolated(Track, State.isolated);
 	overhead(Track, State.overhead);
+	Track.m_uneven = State.uneven;
+	Track.m_unevenup = State.unevenup;
+	Track.m_unevenside = State.unevenside;
+	Track.m_unevencross = State.unevencross;
+	Track.m_jointdip = State.jointdip;
 	Track.m_sleeper_enabled = State.sleepers;
 	Track.m_sleeper_frequency = State.sleeper_frequency;
 	Track.m_sleeper_model_name = State.sleeper_model;
@@ -2350,6 +2360,16 @@ void write_ending(std::ostream &Text, TTrack const &Style)
 {
 	if ((Style.iCategoryFlag & 15) == 1 && false == Style.m_profile1.first.empty())
 		Text << "railprofile " << Style.m_profile1.first << ' ';
+	if (Style.m_uneven > 0.f)
+		Text << "uneven " << Style.m_uneven << ' ';
+	if (Style.m_unevenup >= 0.f)
+		Text << "unevenup " << Style.m_unevenup << ' ';
+	if (Style.m_unevenside >= 0.f)
+		Text << "unevenside " << Style.m_unevenside << ' ';
+	if (Style.m_unevencross >= 0.f)
+		Text << "unevencross " << Style.m_unevencross << ' ';
+	if (Style.m_jointdip >= 0.f)
+		Text << "jointdip " << Style.m_jointdip << ' ';
 	// a piece of the track made from another one stays in its track circuit and under the same overhead line
 	for (auto const *isolated : Style.Isolated)
 		Text << "isolated " << isolated->asName << ' ';
diff --git a/editor/editorTrack.hpp b/editor/editorTrack.hpp
index 43d42762..b6137bd8 100644
--- a/editor/editorTrack.hpp
+++ b/editor/editorTrack.hpp
@@ -55,6 +55,11 @@ class editor_track
 		float texslope{0.9f};
 		std::vector<std::string> isolated;
 		float overhead{-1.f};
+		float uneven{0.f};
+		float unevenup{-1.f};
+		float unevenside{-1.f};
+		float unevencross{-1.f};
+		float jointdip{-1.f};
 		bool sleepers{false};
 		float sleeper_frequency{0.6f};
 		std::string sleeper_model;
diff --git a/lang/editor_pl.po b/lang/editor_pl.po
index 58b30109..a9c61b83 100644
--- a/lang/editor_pl.po
+++ b/lang/editor_pl.po
@@ -861,6 +861,30 @@ msgstr "Odstęp stuków"
 msgid "Quality"
 msgstr "Jakość"
 
+msgid "Unevenness (mm)"
+msgstr "Nierówności toru (mm)"
+
+msgid "Peak deviation of a rail on a 10 m chord. Id-14 limits: 6 mm at 160 km/h, 10 at 120, 18 at 80, 35 at 40.\nWith a sound distance set, the rails also dip at the joints. Joined switches use the lowest of their values"
+msgstr "Największa odchyłka toku szynowego na cięciwie 10 m. Limity Id-14: 6 mm przy 160 km/h, 10 przy 120, 18 przy 80, 35 przy 40.\nPrzy podanym odstępie styków szyny zapadają się też na stykach. Połączone rozjazdy mają najmniejszą ze swoich wartości"
+
+msgid "Up and down (mm)"
+msgstr "W pionie (mm)"
+
+msgid "Sideways (mm)"
+msgstr "W poziomie (mm)"
+
+msgid "Cross level (mm)"
+msgstr "Przechyłka (mm)"
+
+msgid "Set apart from the unevenness, mm. Negative: the unevenness"
+msgstr "Osobno od nierówności, mm. Ujemna: wartość nierówności"
+
+msgid "Dip at rail joints (mm)"
+msgstr "Zapadnięcie na stykach szyn (mm)"
+
+msgid "Depth of the dip at each rail joint, every sound distance. Works with unevenness at 0. Negative: 0.4 of the unevenness"
+msgstr "Głębokość zapadnięcia na każdym styku szyn, co odstęp styków. Działa też przy nierównościach 0. Ujemna: 0,4 nierówności"
+
 msgid "Damage flags"
 msgstr "Flagi uszkodzeń"
 
diff --git a/tests/unit/test_track_uneven.cpp b/tests/unit/test_track_uneven.cpp
new file mode 100644
index 00000000..6333b6ab
--- /dev/null
+++ b/tests/unit/test_track_uneven.cpp
@@ -0,0 +1,152 @@
+#include "stdafx.h"
+#include "doctest.h"
+#include "world/TrackUneven.h"
+
+#include <cmath>
+#include <vector>
+
+namespace {
+
+double deviation(std::vector<double> const &Values)
+{
+	auto mean{0.0};
+	for (auto const value : Values)
+		mean += value;
+	mean /= Values.size();
+	auto sum{0.0};
+	for (auto const value : Values)
+		sum += (value - mean) * (value - mean);
+	return std::sqrt(sum / Values.size());
+}
+
+double peak(std::vector<double> Values)
+{
+	for (auto &value : Values)
+		value = std::abs(value);
+	std::sort(Values.begin(), Values.end());
+	return Values[static_cast<std::size_t>(0.999 * Values.size())];
+}
+
+void add_chord(std::vector<double> &Output, std::vector<double> const &Line, int const Half)
+{
+	for (int i = Half; i + Half < static_cast<int>(Line.size()); ++i)
+		Output.push_back(Line[i] - 0.5 * (Line[i - Half] + Line[i + Half]));
+}
+
+} // namespace
+
+TEST_CASE("uneven track: measures as the Id-14 limits for its value")
+{
+	// appendix 1, class C at 80 km/h: 18 mm vertically, 17 mm sideways, 16 mm of twist on 5 m, gauge +10/-8 mm, 20 mm of cross level, J = 5.3
+	auto const amplitude{track_uneven::stray_per_mm * 18.0 * 1000.0}; // mm
+	double const gauge{1.435};
+	double const step{0.5};
+	int const steps{4000};
+	int const base{10}; // 5 m
+	int const lines{36};
+	double vertical{0.0}, horizontal{0.0}, twist{0.0}, wander{0.0}, level{0.0}, j{0.0}, away{0.0};
+	for (int line = 0; line < lines; ++line)
+	{
+		auto const heading{glm::pi<double>() * (line + 0.37) / lines};
+		glm::dvec3 const start{7919.0 * std::sin(line * 1.7), 0.0, 6577.0 * std::cos(line * 2.3)};
+		glm::dvec3 const along{std::cos(heading), 0.0, std::sin(heading)};
+		glm::dvec3 const across{-along.z, 0.0, along.x};
+		std::vector<double> up[2], side[2], middle;
+		for (int i = 0; i < steps; ++i)
+		{
+			auto const point{start + along * (i * step)};
+			for (int rail = 0; rail < 2; ++rail)
+			{
+				auto const sign{rail == 0 ? 1.0 : -1.0};
+				auto const stray{track_uneven::field(point + across * (sign * 0.5 * gauge))};
+				up[rail].push_back((stray.y - sign * 0.5 * track_uneven::level(point)) * amplitude);
+				side[rail].push_back(glm::dot(stray, across) * amplitude);
+			}
+			middle.push_back(track_uneven::field(point).y * amplitude);
+		}
+		std::vector<double> verticals, horizontals, twists, gauges, levels;
+		for (int rail = 0; rail < 2; ++rail)
+		{
+			add_chord(verticals, up[rail], base);
+			add_chord(horizontals, side[rail], base);
+		}
+		for (int i = 0; i + base < steps; ++i)
+			twists.push_back((up[0][i + base] - up[1][i + base]) - (up[0][i] - up[1][i]));
+		for (int i = 0; i < steps; ++i)
+		{
+			gauges.push_back(side[0][i] - side[1][i]);
+			levels.push_back(up[0][i] - up[1][i]);
+		}
+		vertical += peak(verticals) / lines;
+		horizontal += peak(horizontals) / lines;
+		twist += peak(twists) / lines;
+		wander += peak(gauges) / lines;
+		level += peak(levels) / lines;
+		away += peak(middle) / lines;
+		j += (deviation(verticals) + deviation(horizontals) + deviation(twists) + 0.5 * deviation(gauges)) / 3.5 / lines;
+	}
+	CHECK(vertical == doctest::Approx(18.0).epsilon(0.1));
+	CHECK(horizontal == doctest::Approx(17.0).epsilon(0.2));
+	CHECK(twist == doctest::Approx(16.0).epsilon(0.2));
+	CHECK(wander == doctest::Approx(10.0).epsilon(0.2));
+	CHECK(level == doctest::Approx(20.0).epsilon(0.1));
+	CHECK(j == doctest::Approx(5.3).epsilon(0.2));
+	CHECK(away < 25.0); // appendix 1a: 15 mm off the survey marks
+}
+
+TEST_CASE("uneven track: a place strays the same every time")
+{
+	// no random numbers: changing these changes how every uneven track in every scenery looks
+	glm::dvec3 const place{1234.5, 0.0, -678.9};
+	auto const stray{track_uneven::field(place)};
+	CHECK(stray.x == doctest::Approx(0.309777548158).epsilon(1e-9));
+	CHECK(stray.y == doctest::Approx(-0.295557487607).epsilon(1e-9));
+	CHECK(stray.z == doctest::Approx(-0.328429734019).epsilon(1e-9));
+	CHECK(track_uneven::level(place) == doctest::Approx(0.6 * -0.178598957983).epsilon(1e-9));
+}
+
+TEST_CASE("uneven track: the field stays within its bound")
+{
+	auto most{0.0};
+	for (int i = 0; i < 20000; ++i)
+	{
+		auto const stray{track_uneven::field({i * 3.7 - 30000.0, 0.0, i * -2.9 + 41000.0})};
+		most = std::max({most, std::abs(stray.x), std::abs(stray.y), std::abs(stray.z)});
+	}
+	CHECK(most <= 1.0);
+	CHECK(most > 0.5);
+}
+
+TEST_CASE("uneven track: the value along a track meets its neighbours exactly")
+{
+	double const length{500.0};
+	CHECK(track_uneven::along(20.0, 5.0, 7.0, 0.0, length) == doctest::Approx(5.0));
+	CHECK(track_uneven::along(20.0, 5.0, 7.0, length, length) == doctest::Approx(7.0));
+	CHECK(track_uneven::along(20.0, 5.0, 7.0, 0.5 * length, length) == doctest::Approx(20.0));
+	// equal values stay constant
+	CHECK(track_uneven::along(20.0, 20.0, 20.0, 3.0, length) == doctest::Approx(20.0));
+	// a short track between ends of no value hardly strays
+	CHECK(track_uneven::along(20.0, 0.0, 0.0, 2.5, 5.0) < 1.0);
+	// a switch of more than the track: the track starts at the value of the switch
+	CHECK(track_uneven::along(18.0, 35.0, 18.0, 0.0, length) == doctest::Approx(35.0));
+	CHECK(track_uneven::along(18.0, 35.0, 18.0, track_uneven::fade, length) == doctest::Approx(18.0));
+	// the short piece inside a slip goes with its switches
+	CHECK(track_uneven::along(18.0, 35.0, 35.0, 0.25, 0.5) == doctest::Approx(35.0).epsilon(0.01));
+	// no jump anywhere
+	auto last{track_uneven::along(18.0, 35.0, 0.0, 0.0, length)};
+	for (auto distance{0.25}; distance <= length; distance += 0.25)
+	{
+		auto const value{track_uneven::along(18.0, 35.0, 0.0, distance, length)};
+		REQUIRE(std::abs(value - last) < 0.5);
+		last = value;
+	}
+}
+
+TEST_CASE("uneven track: the rails dip around a joint")
+{
+	CHECK(track_uneven::dip(0.0) == doctest::Approx(1.0));
+	CHECK(track_uneven::dip(1.0) == doctest::Approx(0.75).epsilon(0.01)); // the worst case for rings 2 m apart
+	CHECK(track_uneven::dip(track_uneven::dip_reach) == doctest::Approx(0.0));
+	CHECK(track_uneven::rail_phase(26.0, 25.0) == doctest::Approx(1.0));
+	CHECK(track_uneven::rail_phase(-1.0, 25.0) == doctest::Approx(24.0));
+}
diff --git a/track_uneven_doc.md b/track_uneven_doc.md
new file mode 100644
index 00000000..8cb443ac
--- /dev/null
+++ b/track_uneven_doc.md
@@ -0,0 +1,81 @@
+# Nierówności toru
+
+Opcjonalne atrybuty wpisu toru, przed `endtrack`:
+
+```
+node -1 0 tor1 track normal 100.0 1.435 0.15 25.0 20 0 flat vis
+rail_screw_used1 6 1435mm/tpbps-new2 0.2 0.5 1.1
+0.0 0.2 0.0 0.0
+0.0 0.0 0.0
+0.0 0.0 0.0
+0.0 0.2 100.0 0.0
+0.0
+uneven 18
+unevencross 25
+jointdip 6
+endtrack
+```
+
+| atrybut           | dotyczy               | opis                                                                                  |
+|-------------------|-----------------------|---------------------------------------------------------------------------------------|
+| `uneven <mm>`     | `normal`, `switch`    | największa odchyłka toku szynowego na cięciwie 10 m; 0-100, domyślnie 0               |
+| `unevenup <mm>`   | `normal`, `switch`    | składowa w pionie, osobno od `uneven`                                                 |
+| `unevenside <mm>` | `normal`, `switch`    | składowa w poziomie, osobno od `uneven`                                               |
+| `unevencross <mm>`| `normal`              | składowa przechyłki, osobno od `uneven`; rozjazd jej nie ma                           |
+| `jointdip <mm>`   | `normal`              | głębokość zapadnięcia na styku szyn; 0-100, domyślnie 0,4 składowej w pionie          |
+
+Składowa niepodana przyjmuje wartość `uneven`. Na przykład sam bok to `unevenside 30`, a same zapadnięcia na stykach to `jointdip 6`.
+
+Wszystkie są też w edytorze, w panelu toru, w sekcji „Ride and sound”. Na drogach, rzekach i obrotnicach są ignorowane.
+
+## Jaką wartość wybrać
+
+`uneven` odpowiada kolumnie „nierówności pionowe” z instrukcji PLK Id-14, załącznik 1 (klasa C):
+
+| prędkość [km/h] | 20 | 40 | 60 | 80 | 100 | 120 | 160 |
+|-----------------|----|----|----|----|-----|-----|-----|
+| `uneven` [mm]   | 50 | 35 | 25 | 18 | 14  | 10  | 6   |
+
+Tor w dobrym stanie to według instrukcji połowa tej wartości (klasa A), w dostatecznym 3/4 (klasa B).
+
+Tor z `uneven 18` mierzy się tak (`tests/unit/test_track_uneven.cpp`), w nawiasie limit Id-14 dla 80 km/h:
+
+| parametr                  | wynik   | Id-14   |
+|---------------------------|---------|---------|
+| nierówności pionowe       | 18 mm   | 18 mm   |
+| nierówności poziome       | 19 mm   | 17 mm   |
+| wichrowatość na bazie 5 m | 17 mm   | 16 mm   |
+| szerokość toru            | ±10 mm  | +10/-8 mm |
+| przechyłka                | 20 mm   | 20 mm   |
+| wskaźnik J                | 6,1     | 5,3     |
+
+## Jak to działa
+
+Nierówność to pole przesunięć zależne od położenia na mapie, złożone z fal o długości 5-42 m. Nie ma w nim losowania: to samo miejsce wygina się tak samo przy każdym uruchomieniu. Przesunięty tor dostaje fale z nowego miejsca.
+
+Każda składowa łączy się osobno:
+
+- **Tor z torem:** na styku obowiązuje mniejsza z dwóch wartości, a każdy tor dochodzi do niej płynnie na 20 m. Wolny koniec toru leży w projekcie.
+- **Rozjazd:** wszystkie jego drogi mają jedną wartość. Rozjazdy złączone bezpośrednio przyjmują najmniejszą ze swoich. Dołączony tor dochodzi do wartości rozjazdu, także większej od własnej. Tor bez danej składowej trzyma w niej cały rozjazd w projekcie.
+- **Styki:** zapadnięcia są co `fSoundDistance`, na długości 6 m, i biegną dalej przez kolejne tory o tym samym odstępie. Stukot osi wypada w miejscu zapadnięcia. Przy odstępie 6 m lub mniejszym oraz na rozjazdach zapadnięć nie ma.
+- **Przechyłka:** dolicza się do projektowej. Na rozjazdach tylko ta wynikająca z fal, bez osobnego siadania toków.
+
+Za nierównością idą szyny, podsypka, `sleepermodel`, osie, przechył pudła i bujanie kabiny.
+
+Nie idą za nią modele z includów (np. napędy i podkłady rozjazdów), teren ani sieć trakcyjna, więc przy dużych wartościach szyna rozjeżdża się z takim modelem o kilka centymetrów.
+
+Fizyka bierze promień łuku i pochylenie z projektu, więc nierówności nie zmieniają tych wartości, a do wykolejeń dokładają tylko przechyłkę, ok. 0,06 m/s² przy `uneven 18` wobec progu ok. 3,2 m/s².
+
+## Wydajność
+
+Tor z nierównością ma geometrię co 2 m zamiast co 10 m na prostych. Rozjazdy zachowują swój podział.
+
+Zmierzone (kamera w ruchu lub kabina, 1920×1080):
+
+| scena                                 | bez flag           | z flagami 18/35    |
+|---------------------------------------|--------------------|--------------------|
+| Bałtyk, 56 km torów: wierzchołki      | 0,56 mln (ok. 27 MB) | 2,17 mln (ok. 104 MB) |
+| Bałtyk: najdłuższa klatka w przelocie | 31,5 ms            | 64 ms              |
+| `td.scn`, jazda 120 km/h: klatka      | 2,73 ms            | 2,93 ms            |
+
+Koszt rośnie z liczbą oflagowanych torów, a najdłuższe klatki pojawiają się przy budowaniu geometrii kolejnych sekcji. Sama jazda po takim torze praktycznie nie kosztuje: ok. 0,3 µs na oś w kroku fizyki.
diff --git a/vehicle/DynObj.cpp b/vehicle/DynObj.cpp
index 32ba307f..83354288 100644
--- a/vehicle/DynObj.cpp
+++ b/vehicle/DynObj.cpp
@@ -3627,6 +3627,7 @@ bool TDynamicObject::Update(double dt, double dt1)
             if( dRailLength > 0.0 ) {
                 for( auto &axle : m_axlesounds ) {
                     axle.distance = axle.offset;
+                    axle.atjoints = false;
                 }
             }
             dRailLength = MyTrack->fSoundDistance;
@@ -3660,9 +3661,19 @@ bool TDynamicObject::Update(double dt, double dt1)
                             1 :
                             ctOwner->Vehicle()->DirectionGet() == DirectionGet() ? 1 : -1 ) };
                     for( auto &axle : m_axlesounds ) {
-                        axle.distance += dDOMoveLen * directioninconsist;
-                        if( axle.distance < 0
-                         || axle.distance > dRailLength ) {
+                        // on a track with dipping joints the clatter comes from them, elsewhere the axle counts a rail off itself
+                        auto const railphase { Axle0.RailPhase( axle.offset - 0.5 * fAxleDist ) };
+                        auto crossed { false };
+                        if( railphase >= 0.0 ) {
+                            crossed = axle.atjoints && std::abs( railphase - axle.distance ) > 0.5 * dRailLength;
+                            axle.distance = railphase;
+                        }
+                        else {
+                            axle.distance += dDOMoveLen * directioninconsist;
+                            crossed = axle.distance < 0 || axle.distance > dRailLength;
+                        }
+                        axle.atjoints = ( railphase >= 0.0 );
+                        if( crossed ) {
                             axle.distance = clamp_circular( axle.distance, dRailLength );
                             if( MoverParameters->Vel > 0.1 ) {
                                 // NOTE: for combined clatter sound we supply 1/100th of actual value, as the sound module converts does the opposite, converting received (typically) 0-1 values to 0-100 range
@@ -8035,6 +8046,12 @@ TDynamicObject::update_shake( double const Timedelta ) {
                 -MoverParameters->AccN * Timedelta * 5.0 * Global.ShakingMultiplierRL, // highlight side sway
                 -MoverParameters->AccVert * Timedelta * Global.ShakingMultiplierUD,
                 -MoverParameters->AccSVBased * Timedelta * 1.5 * Global.ShakingMultiplierBF); // accent acceleration/deceleration
+            // unevenness of the track under the outer axles
+            auto const ride { 0.5 * ( Axle0.UnevenBend() + Axle1.UnevenBend() ) * ( MoverParameters->V * MoverParameters->V ) };
+            shakevector += glm::dvec3(
+                -glm::dot( ride, vLeft ) * Timedelta * 5.0 * Global.ShakingMultiplierRL,
+                -ride.y * Timedelta * Global.ShakingMultiplierUD,
+                0.0 );
         }
 
         auto shake { 1.25 * ShakeSpring.ComputateForces( shakevector, ShakeState.offset ) };
diff --git a/vehicle/DynObj.h b/vehicle/DynObj.h
index 36335a32..1bc50b1d 100644
--- a/vehicle/DynObj.h
+++ b/vehicle/DynObj.h
@@ -402,6 +402,7 @@ private:
         double distance; // distance to rail joint
         double offset; // axle offset from centre of the vehicle
         sound_source clatter; // clatter emitter
+        bool atjoints { false }; // distance comes from TTrack::rail_phase
     };
 
     struct powertrain_sounds {
diff --git a/world/Segment.cpp b/world/Segment.cpp
index 69886f42..ad817b5e 100644
--- a/world/Segment.cpp
+++ b/world/Segment.cpp
@@ -118,6 +118,10 @@ bool TSegment::Init(glm::dvec3 &NewPoint1, glm::dvec3 NewCPointOut, glm::dvec3 N
     fStoop = std::atan2(Point2.y - Point1.y, fLength); // pochylenie toru prostego, żeby nie liczyć wielokrotnie
 
     fStep = fNewStep;
+    if( m_uneven && pOwner->eType != tt_Switch ) {
+        // dense enough for the waves; a switch keeps its division, the blades depend on it
+        fStep = std::min( fStep, 2.0 );
+    }
     // NOTE: optionally replace this part with the commented version, after solving geometry issues with double switches
     if( pOwner->eType == tt_Switch
      && fStep * (3.0 * Global.SplineFidelity) > fLength ) {
@@ -366,6 +370,52 @@ Math3D::vector3 TSegment::GetPoint(double const fDistance) const
 */
 
 void TSegment::RaPositionGet(double const fDistance, glm::dvec3 &position, glm::vec3 &rotation) const {
+    design_position( fDistance, position, rotation );
+    if( false == m_uneven ) {
+        return;
+    }
+    // direction and slope stay as designed: the physics takes the curve radius and the grade from them
+    auto const gauge { std::max( std::abs( pOwner->fTrackWidth ), 0.1f ) };
+    glm::dvec3 const across { -std::cos( rotation.z ), 0.0, -std::sin( rotation.z ) };
+    auto const amount { pOwner->uneven_at( fDistance ) };
+    rotation.x += static_cast<float>( track_uneven::stray_per_mm * (
+        amount.up * track_uneven::roll( position, across, gauge )
+      + amount.cross * track_uneven::level( position ) / gauge ) );
+    position += stray( position, fDistance );
+}
+
+glm::dvec3 TSegment::stray( glm::dvec3 const &Point, double const Distance ) const {
+    auto const amount { pOwner->uneven_at( Distance ) };
+    auto const field { track_uneven::field( Point ) };
+    glm::dvec3 result { field.x * amount.side, field.y * amount.up, field.z * amount.side };
+    result *= track_uneven::stray_per_mm;
+    result.y -= pOwner->joint_dip( Distance );
+    return result;
+}
+
+glm::dvec3 TSegment::uneven_bend( double const Distance ) const {
+    if( false == m_uneven ) {
+        return glm::dvec3 { 0.0 };
+    }
+    // over about a bogie; FastGetTFromS extrapolates past the ends of the path
+    auto const reach { 1.5 };
+    auto const strayed = [&]( double const At ) {
+        return stray( FastGetPoint( FastGetTFromS( At ) ), At ); };
+    return ( strayed( Distance + reach ) - 2.0 * strayed( Distance ) + strayed( Distance - reach ) ) / ( reach * reach );
+}
+
+void TSegment::settle_vertex( gfx::basic_vertex &Vertex, glm::dvec3 const &Origin, glm::vec3 const &Position, glm::vec3 const &Parallel, double const Distance ) const {
+    if( false == m_uneven ) {
+        return;
+    }
+    // the rails settling apart turn about the middle of the track, what's outside them follows the rail
+    auto const gauge { std::max( std::abs( pOwner->fTrackWidth ), 0.1f ) };
+    auto const across { std::clamp( glm::dot( Vertex.position - Position, Parallel ), -0.5f * gauge, 0.5f * gauge ) };
+    Vertex.position.y -= static_cast<float>( track_uneven::stray_per_mm * pOwner->uneven_at( Distance ).cross * track_uneven::level( Origin + glm::dvec3 { Position } ) * across / gauge );
+    Vertex.position += glm::vec3 { stray( Origin + glm::dvec3 { Vertex.position }, Distance ) };
+}
+
+void TSegment::design_position(double const fDistance, glm::dvec3 &position, glm::vec3 &rotation) const {
     if (bCurve) {
         // można by wprowadzić uproszczony wzór dla okręgów płaskich
         auto const t = FastGetTFromS(fDistance); // aproksymacja dystansu na krzywej Beziera na parametr (t)
@@ -500,6 +550,7 @@ bool TSegment::RenderLoft( gfx::vertex_array &Output, glm::dvec3 const &Origin,
                         pt,
                         glm::normalize( norm ),
                         glm::vec2 { ( jmm1 * ShapePoints[ j ].texture.x + m1 * ShapePoints[ j + iNumShapePoints ].texture.x ) / texturescale, tv1 } );
+                    settle_vertex( Output.back(), Origin, pos1, parallel1, s - step );
                 }
                 // jeśli jest wskaźnik do tablicy
                 if (p && *p && !j) // to dla pierwszego punktu
@@ -518,6 +569,7 @@ bool TSegment::RenderLoft( gfx::vertex_array &Output, glm::dvec3 const &Origin,
                         pt,
                         glm::normalize( norm ),
                         glm::vec2 { ( jmm2 * ShapePoints[ j ].texture.x + m2 * ShapePoints[ j + iNumShapePoints ].texture.x ) / texturescale, tv2 } );
+                    settle_vertex( Output.back(), Origin, pos2, parallel2, s );
                 }
                 // jeśli jest wskaźnik do tablicy
                 // to dla pierwszego punktu
@@ -540,6 +592,7 @@ bool TSegment::RenderLoft( gfx::vertex_array &Output, glm::dvec3 const &Origin,
                         pt,
                         glm::normalize( norm ),
                         glm::vec2 { ShapePoints[ j ].texture.x / texturescale, tv1 } );
+                    settle_vertex( Output.back(), Origin, pos1, parallel1, s - step );
 
                     pt = parallel2 * ( jmm2 * ( ShapePoints[ j ].position.x - fOffsetX.first ) + m2 * ( ShapePoints[ j ].position.x - fOffsetX.second ) ) + pos2;
                     pt.y += ShapePoints[ j ].position.y;
@@ -550,6 +603,7 @@ bool TSegment::RenderLoft( gfx::vertex_array &Output, glm::dvec3 const &Origin,
                         pt,
                         glm::normalize( norm ),
                         glm::vec2 { ShapePoints[ j ].texture.x / texturescale, tv2 } );
+                    settle_vertex( Output.back(), Origin, pos2, parallel2, s );
                 }
             }
         }
diff --git a/world/Segment.h b/world/Segment.h
index a3c83ade..492cab94 100644
--- a/world/Segment.h
+++ b/world/Segment.h
@@ -47,6 +47,7 @@ class TSegment
     glm::dvec3 Point2;
     float fRoll1 { 0.f };
     float fRoll2 { 0.f }; // przechyłka na końcach
+    bool m_uneven { false }; // see TrackUneven.h
     double fLength { -1.0 }; // długość policzona
     std::vector<double> fTsBuffer; // wartości parametru krzywej t dla równych odcinków s
     std::vector<double> fTsSlope; // nachylenie dt/du (= dt/ds * fStep) w tych samych punktach
@@ -67,6 +68,12 @@ class TSegment
 	glm::dvec3 RaInterpolate(double const t) const;
 	glm::dvec3 RaInterpolate0(double const t) const;
 
+    // moves a lofted vertex with the unevenness of the track
+    void settle_vertex( gfx::basic_vertex &Vertex, glm::dvec3 const &Origin, glm::vec3 const &Position, glm::vec3 const &Parallel, double const Distance ) const;
+    // displacement of a point by the unevenness, at a distance along the path
+    glm::dvec3 stray( glm::dvec3 const &Point, double const Distance ) const;
+    void design_position( double const fDistance, glm::dvec3 &position, glm::vec3 &rotation ) const;
+
 public:
     bool bCurve = false;
 
@@ -106,6 +113,13 @@ public:
 	/// <param name="position">Calculated position</param>
 	/// <param name="rotation">Calculated rotation</param>
 	void RaPositionGet(double const fDistance, glm::dvec3 &position, glm::vec3 &rotation) const;
+    // call before Init, it sets the density of the geometry
+    void
+        set_uneven( bool const Uneven ) {
+            m_uneven = Uneven; }
+    // second derivative of the displacement along the path; times speed squared: acceleration of an axle
+    glm::dvec3
+        uneven_bend( double const Distance ) const;
 	glm::dvec3 FastGetPoint(double const t) const;
     inline
     glm::dvec3
diff --git a/world/Track.cpp b/world/Track.cpp
index f1a29798..ff5a378a 100644
--- a/world/Track.cpp
+++ b/world/Track.cpp
@@ -47,6 +47,7 @@ TIsolated *TIsolated::pRoot = nullptr;
 
 TTrack::profiles_array TTrack::m_profiles;
 TTrack::profiles_map TTrack::m_profilesmap;
+int TTrack::s_layoutstamp { 0 };
 
 TSwitchExtension::TSwitchExtension(TTrack *owner, int const what)
 { // na początku wszystko puste
@@ -325,6 +326,7 @@ void TTrack::ConnectPrevPrev(TTrack *pTrack, int typ)
 { //łączenie torów - Point1 własny do Point1 cudzego
     if (pTrack)
     { //(pTrack) może być zwrotnicą, a (this) tylko zwykłym odcinkiem
+        ++s_layoutstamp;
         trPrev = pTrack;
         iPrevDirection = pTrack->eType == tt_Switch ? 0 : typ & 2;
         pTrack->trPrev = this;
@@ -335,6 +337,7 @@ void TTrack::ConnectPrevNext(TTrack *pTrack, int typ)
 { //łaczenie torów - Point1 własny do Point2 cudzego
     if (pTrack)
     {
+        ++s_layoutstamp;
         trPrev = pTrack;
         iPrevDirection = typ | 1; // 1:zwykły lub pierwszy zwrotnicy, 3:drugi zwrotnicy
         pTrack->trNext = this;
@@ -354,6 +357,7 @@ void TTrack::ConnectNextPrev(TTrack *pTrack, int typ)
 { //łaczenie torów - Point2 własny do Point1 cudzego
     if (pTrack)
     {
+        ++s_layoutstamp;
         trNext = pTrack;
         iNextDirection = pTrack->eType == tt_Switch ? 0 : typ & 2;
         pTrack->trPrev = this;
@@ -373,6 +377,7 @@ void TTrack::ConnectNextNext(TTrack *pTrack, int typ)
 { //łaczenie torów - Point2 własny do Point2 cudzego
     if (pTrack)
     {
+        ++s_layoutstamp;
         trNext = pTrack;
         iNextDirection = typ | 1; // 1:zwykły lub pierwszy zwrotnicy, 3:drugi zwrotnicy
         pTrack->trNext = this;
@@ -633,6 +638,27 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
                 m_profile1 = fetch_track_rail_profile( railprofile );
             }
         }
+        else if( str == "uneven" ) {
+            // uneven <mm>: see TrackUneven.h
+            auto const uneven { parser->getToken<float>() };
+            if( ( eType == tt_Normal || eType == tt_Switch ) && iCategoryFlag == 1 ) {
+                m_uneven = std::clamp( uneven, 0.f, track_uneven::most );
+            }
+        }
+        else if( str == "unevenup" || str == "unevenside" || str == "unevencross" ) {
+            // the components of uneven set apart, mm
+            auto const value { parser->getToken<float>() };
+            if( ( eType == tt_Normal || eType == tt_Switch ) && iCategoryFlag == 1 ) {
+                ( str == "unevenup" ? m_unevenup : str == "unevenside" ? m_unevenside : m_unevencross ) = std::clamp( value, 0.f, track_uneven::most );
+            }
+        }
+        else if( str == "jointdip" ) {
+            // jointdip <mm>: depth of the dip at rail joints, with or without uneven
+            auto const jointdip { parser->getToken<float>() };
+            if( eType == tt_Normal && iCategoryFlag == 1 ) {
+                m_jointdip = std::clamp( jointdip, 0.f, track_uneven::most );
+            }
+        }
         else if( str == "friction" ) {
             // memory cell holding friction value modifiers
             m_friction.first = parser->getToken<std::string>();
@@ -674,6 +700,10 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
         *parser >> token;
 		str = token;
     }
+    // the segments were made before the attributes were read, and unevenness changes them
+    if( is_uneven() ) {
+        init_segments( false );
+    }
     // alternatywny zapis nazwy odcinka izolowanego - po znaku "@" w nazwie toru
     if ((i = m_name.find("@")) != std::string::npos && i < m_name.length())
     {
@@ -687,6 +717,159 @@ void TTrack::Load(cParser *parser, glm::dvec3 const &pOrigin)
     // to a stale origin and the renderer would draw sleepers in the wrong place).
 }
 
+track_uneven::amounts TTrack::uneven_declared() const {
+
+    return {
+        m_unevenup >= 0.f ? m_unevenup : m_uneven,
+        m_unevenside >= 0.f ? m_unevenside : m_uneven,
+        eType != tt_Normal ? 0.f : m_unevencross >= 0.f ? m_unevencross : m_uneven };
+}
+
+bool TTrack::is_uneven() const {
+
+    auto const declared { uneven_declared() };
+    return declared.up > 0.0 || declared.side > 0.0 || declared.cross > 0.0 || joint_depth() > 0.0;
+}
+
+track_uneven::amounts TTrack::uneven_at( double const Distance ) const {
+
+    if( eType == tt_Switch ) {
+        return switch_uneven();
+    }
+    auto const own { uneven_declared() };
+    auto const atend = [&]( TTrack const *Other ) -> track_uneven::amounts {
+        if( Other == nullptr ) {
+            return {};
+        }
+        if( Other->eType == tt_Switch ) {
+            return Other->switch_uneven();
+        }
+        auto const theirs { Other->uneven_declared() };
+        return { std::min( own.up, theirs.up ), std::min( own.side, theirs.side ), std::min( own.cross, theirs.cross ) }; };
+    auto const start { atend( trPrev ) };
+    auto const end { atend( trNext ) };
+    return {
+        track_uneven::along( own.up, start.up, end.up, Distance, Length() ),
+        track_uneven::along( own.side, start.side, end.side, Distance, Length() ),
+        track_uneven::along( own.cross, start.cross, end.cross, Distance, Length() ) };
+}
+
+track_uneven::amounts TTrack::switch_uneven() const {
+
+    if( m_switchstray.stamp == s_layoutstamp ) {
+        return m_switchstray.value;
+    }
+    std::vector<TTrack const *> group { this };
+    auto least { uneven_declared() };
+    for( std::size_t index = 0; index < group.size(); ++index ) {
+        auto const &extension { *group[ index ]->SwitchExtension };
+        for( auto const *other : { extension.pPrevs[ 0 ], extension.pPrevs[ 1 ], extension.pNexts[ 0 ], extension.pNexts[ 1 ] } ) {
+            if( other == nullptr ) {
+                continue;
+            }
+            auto const theirs { other->uneven_declared() };
+            if( other->eType == tt_Switch && other->SwitchExtension ) {
+                least.up = std::min( least.up, theirs.up );
+                least.side = std::min( least.side, theirs.side );
+                if( std::find( group.begin(), group.end(), other ) == group.end() ) {
+                    group.push_back( other );
+                }
+            }
+            else {
+                // a track with none of a component keeps to its design in it, any other comes to the value of the switch
+                if( theirs.up <= 0.0 ) { least.up = 0.0; }
+                if( theirs.side <= 0.0 ) { least.side = 0.0; }
+            }
+        }
+    }
+    for( auto const *track : group ) {
+        track->m_switchstray = { least, s_layoutstamp };
+    }
+    return least;
+}
+
+double TTrack::joint_depth() const {
+
+    if( eType != tt_Normal ) {
+        return 0.0;
+    }
+    return ( m_jointdip >= 0.f ? m_jointdip : track_uneven::dip_share * uneven_declared().up );
+}
+
+double TTrack::joint_dip( double const Distance ) const {
+
+    auto const phase { rail_phase( Distance ) };
+    if( phase < 0.0 ) {
+        return 0.0;
+    }
+    auto const fromjoint { std::min( phase, fSoundDistance - phase ) };
+    if( fromjoint >= track_uneven::dip_reach ) {
+        return 0.0;
+    }
+    auto const depth { joint_depth() };
+    auto const atend = [&]( TTrack const *Other ) {
+        return ( Other == nullptr || Other->fSoundDistance != fSoundDistance ? 0.0 : std::min( depth, Other->joint_depth() ) ); };
+    return 0.001 * track_uneven::dip( fromjoint ) * track_uneven::along( depth, atend( trPrev ), atend( trNext ), Distance, Length() );
+}
+
+double TTrack::rail_phase( double const Distance ) const {
+
+    if( joint_depth() <= 0.0 || fSoundDistance <= 2.0 * track_uneven::dip_reach ) {
+        return -1.0;
+    }
+    if( m_railrun.stamp != s_layoutstamp ) {
+        settle_rail_run();
+    }
+    return track_uneven::rail_phase( m_railrun.origin + m_railrun.way * Distance, fSoundDistance );
+}
+
+void TTrack::settle_rail_run() const {
+
+    // the next track of the run past an end of a track, and which of its ends is joined there
+    auto const onward = []( TTrack const &Track, int const End, int &Joined ) -> TTrack const * {
+        auto const *other { End == 0 ? Track.trPrev : Track.trNext };
+        if( other == nullptr || other == &Track || other->joint_depth() <= 0.0 || other->fSoundDistance != Track.fSoundDistance ) {
+            return nullptr;
+        }
+        Joined = ( End == 0 ? Track.iPrevDirection : Track.iNextDirection ) & 1;
+        return other; };
+    // walks from this track to an end of the run
+    auto const walk = [&]( int &End ) {
+        auto const *track { this };
+        int joined { 0 };
+        for( int step = 0; step < 1000000; ++step ) {
+            auto const *next { onward( *track, End, joined ) };
+            if( next == nullptr || next == this ) {
+                break;
+            }
+            track = next;
+            End = 1 - joined;
+        }
+        return track; };
+    auto const place = []( TTrack const &Track, int const End ) {
+        auto const point { End == 0 ? Track.Segment->FastGetPoint_0() : Track.Segment->FastGetPoint_1() };
+        return std::make_pair( point.x, point.z ); };
+
+    // start at the end with the lesser coordinates, to get the same joints from any track of the run
+    int end { 0 };
+    int otherend { 1 };
+    auto const *track { walk( end ) };
+    auto const *other { walk( otherend ) };
+    if( place( *other, otherend ) < place( *track, end ) ) {
+        track = other;
+        end = otherend;
+    }
+    auto along { 0.0 };
+    while( track != nullptr && track->m_railrun.stamp != s_layoutstamp ) {
+        auto const length { track->Length() };
+        track->m_railrun = { end == 0 ? along : along + length, end == 0 ? 1.0 : -1.0, s_layoutstamp };
+        along += length;
+        int joined { 0 };
+        track = onward( *track, 1 - end, joined );
+        end = joined;
+    }
+}
+
 void TTrack::update_location() {
 
     location( (
@@ -705,6 +888,14 @@ void TTrack::init_segments( bool const Initial ) {
     fTexHeight1 -= fTexHeightOffset;
     fTexHeightOffset = 0.f;
     iTrapezoid = 0;
+    ++s_layoutstamp;
+    if( eType == tt_Switch && SwitchExtension ) {
+        SwitchExtension->Segments[ 0 ]->set_uneven( is_uneven() );
+        SwitchExtension->Segments[ 1 ]->set_uneven( is_uneven() );
+    }
+    else if( Segment ) {
+        Segment->set_uneven( is_uneven() );
+    }
 
     switch (eType) {
         // Ra: łuki segmentowane co 5m albo 314-kątem foremnym
@@ -1351,6 +1542,8 @@ glm::vec3 TTrack::get_nearest_point(const glm::dvec3 &point) const
 // wypełnianie tablic VBO
 void TTrack::rebuild_geometry( gfx::geometrybank_handle const &Bank ) {
 
+    ++s_layoutstamp;
+
     Geometry1.clear();
     Geometry2.clear();
     if( SwitchExtension ) {
@@ -2445,6 +2638,21 @@ TTrack::export_as_text_( std::ostream &Output ) const {
      && false == m_profile1.first.empty() ) {
         Output << "railprofile " << m_profile1.first << ' ';
     }
+    if( m_uneven > 0.f ) {
+        Output << "uneven " << m_uneven << ' ';
+    }
+    if( m_unevenup >= 0.f ) {
+        Output << "unevenup " << m_unevenup << ' ';
+    }
+    if( m_unevenside >= 0.f ) {
+        Output << "unevenside " << m_unevenside << ' ';
+    }
+    if( m_unevencross >= 0.f ) {
+        Output << "unevencross " << m_unevencross << ' ';
+    }
+    if( m_jointdip >= 0.f ) {
+        Output << "jointdip " << m_jointdip << ' ';
+    }
     if( false == m_friction.first.empty() ) {
         Output << "friction " << m_friction.first << ' ';
     }
diff --git a/world/Track.h b/world/Track.h
index 72a6b7ff..ac6d1425 100644
--- a/world/Track.h
+++ b/world/Track.h
@@ -19,6 +19,7 @@ http://mozilla.org/MPL/2.0/.
 
 #include "utilities/Classes.h"
 #include "world/Segment.h"
+#include "world/TrackUneven.h"
 #include "model/material.h"
 #include "scene/scenenode.h"
 #include "utilities/Names.h"
@@ -238,6 +239,12 @@ public:
     TEnvironmentType eEnvironment = e_flat; // dźwięk i oświetlenie
     int iAction = 0; // czy modyfikowany eventami (specjalna obsługa przy skanowaniu)
     float fOverhead = -1.0; // można normalnie pobierać prąd (0 dla jazdy bezprądowej po danym odcinku, >0-z opuszczonym i ograniczeniem prędkości)
+    float m_uneven { 0.f }; // mm, see TrackUneven.h; plain tracks and switches
+    // the components set apart from m_uneven, mm; negative: m_uneven. Cross level on plain tracks only
+    float m_unevenup { -1.f };
+    float m_unevenside { -1.f };
+    float m_unevencross { -1.f };
+    float m_jointdip { -1.f }; // depth of the dip at rail joints, mm; negative: from m_uneven; plain tracks only
 private:
     double fVelocity = -1.0; // ograniczenie prędkości // prędkość dla AI (powyżej rośnie prawdopowobieństwo wykolejenia)
 public:
@@ -339,6 +346,15 @@ public:
     void VelocitySet(float v);
     double VelocityGet();
     float Friction() const;
+    // the unevenness the track declares
+    track_uneven::amounts uneven_declared() const;
+    bool is_uneven() const;
+    // the unevenness at a distance along the track, meeting the tracks joined at its ends
+    track_uneven::amounts uneven_at( double const Distance ) const;
+    double joint_depth() const; // mm
+    double joint_dip( double const Distance ) const; // m
+    // distance from the rail joint behind; negative: the track has no joints that dip
+    double rail_phase( double const Distance ) const;
     void ConnectionsLog();
     bool DoubleSlip() const;
     static void fetch_default_profiles();
@@ -370,6 +386,22 @@ private:
     void create_track_rail_profile( gfx::vertex_array &Right, gfx::vertex_array &Left );
     void create_track_blade_profile( gfx::vertex_array &Right, gfx::vertex_array &Left );
     void create_track_bed_profile( gfx::vertex_array &Output, TTrack const *Previous, TTrack const *Next );
+    // rail joints run on across joined tracks, however the line is cut into them, so the clatter keeps its rhythm
+    struct rail_run {
+        double origin { 0.0 }; // position along the run of Point1
+        double way { 1.0 }; // direction of the path along the run
+        int stamp { -1 };
+    };
+    void settle_rail_run() const;
+    mutable rail_run m_railrun;
+    // one value along all paths of a switch: the lowest of the switches joined, 0 next to a track with none
+    track_uneven::amounts switch_uneven() const;
+    struct switch_stray {
+        track_uneven::amounts value;
+        int stamp { -1 };
+    };
+    mutable switch_stray m_switchstray;
+    static int s_layoutstamp; // bumped when tracks are joined or changed, invalidates the two above
     void create_road_profile( gfx::vertex_array &Output, bool const Forcetransition = false );
     void create_road_side_profile( gfx::vertex_array &Right, gfx::vertex_array &Left, gfx::vertex_array const &Road, bool const Forcetransition = false );
     /// <summary>
diff --git a/world/TrackUneven.h b/world/TrackUneven.h
new file mode 100644
index 00000000..7486cea2
--- /dev/null
+++ b/world/TrackUneven.h
@@ -0,0 +1,125 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <algorithm>
+#include <array>
+#include <cmath>
+#include <glm/glm.hpp>
+#include <glm/gtc/constants.hpp>
+
+// Track unevenness: a displacement field over the plan of the scenery, so everything at one place moves together: joined tracks, the
+// paths of a switch, sleepers, axles. Waves 5-42 m long, shares after the German track spectrum with the long waves cut down.
+// The "uneven" value is the peak deviation of a rail on a 10 m chord, as in PLK Id-14 appendix 1; see test_track_uneven.cpp.
+namespace track_uneven {
+
+inline constexpr float most { 100.f }; // largest value of the attributes, mm
+inline constexpr double stray_per_mm { 0.00145 }; // field amplitude per mm of "uneven", m
+inline constexpr double cross_share { 0.6 }; // share of the field amplitude the rails settle apart by
+inline constexpr double fade { 20.0 }; // length over which a track goes from the value at its end to its own, m
+inline constexpr double dip_share { 0.4 }; // joint dip depth per mm of "uneven", mm
+inline constexpr double dip_reach { 3.0 }; // reach of the dip on each side of a joint, m
+
+// the value of each component of the unevenness, mm
+struct amounts {
+    double up { 0.0 };
+    double side { 0.0 };
+    double cross { 0.0 };
+};
+
+struct wave {
+    double x;
+    double z;
+    double phase;
+    double share;
+};
+
+template <std::size_t Count>
+using wave_set = std::array<wave, Count>;
+
+// the waves run in all directions of the plan, so no direction of a track is favoured
+template <std::size_t Count>
+wave_set<Count> make_waves( double const Turn, std::array<double, Count> const &Lengths, std::array<double, Count> const &Shares ) {
+
+    auto const golden { glm::pi<double>() * ( 3.0 - std::sqrt( 5.0 ) ) };
+    wave_set<Count> result {};
+    for( std::size_t i = 0; i < Count; ++i ) {
+        auto const number { glm::two_pi<double>() / Lengths[ i ] };
+        auto const heading { Turn + golden * i };
+        result[ i ] = { number * std::cos( heading ), number * std::sin( heading ), golden * ( i + 1 ) * ( 1.0 + 3.0 * Turn ), Shares[ i ] };
+    }
+    return result;
+}
+
+inline constexpr std::array<double, 8> wave_lengths { 5.3, 7.1, 9.7, 13.1, 17.9, 23.9, 31.7, 41.9 };
+inline constexpr std::array<double, 8> wave_shares { 0.0721, 0.0997, 0.1344, 0.1703, 0.1549, 0.1386, 0.1226, 0.1074 };
+
+inline wave_set<8> const up_waves { make_waves( 0.0, wave_lengths, wave_shares ) };
+inline wave_set<8> const x_waves { make_waves( 1.1, wave_lengths, wave_shares ) };
+inline wave_set<8> const z_waves { make_waves( 2.3, wave_lengths, wave_shares ) };
+// long waves only: with the short ones the cross level reaching its limit would break the limit of twist
+inline wave_set<3> const cross_waves { make_waves<3>( 0.7, { 23.9, 31.7, 41.9 }, { 1.0 / 3.0, 1.0 / 3.0, 1.0 / 3.0 } ) };
+
+template <std::size_t Count>
+double sum( wave_set<Count> const &Waves, glm::dvec3 const &Point ) {
+
+    auto total { 0.0 };
+    for( auto const &wave : Waves ) {
+        total += wave.share * std::sin( wave.x * Point.x + wave.z * Point.z + wave.phase );
+    }
+    return total;
+}
+
+// displacement at the point for an amplitude of 1, each axis within +-1
+inline glm::dvec3 field( glm::dvec3 const &Point ) {
+
+    return { sum( x_waves, Point ), sum( up_waves, Point ), sum( z_waves, Point ) };
+}
+
+// how much lower the right rail lies by settling apart, for an amplitude of 1. Follows the middle of a path, so plain tracks only
+inline double level( glm::dvec3 const &Point ) {
+
+    return cross_share * sum( cross_waves, Point );
+}
+
+// roll made by the field for an amplitude of 1; positive lowers the rail towards Across, as the roll of a path
+inline double roll( glm::dvec3 const &Point, glm::dvec3 const &Across, double const Gauge ) {
+
+    return ( sum( up_waves, Point - Across * ( 0.5 * Gauge ) ) - sum( up_waves, Point + Across * ( 0.5 * Gauge ) ) ) / Gauge;
+}
+
+// value at a distance along a track: Full inside, exactly Atstart and Atend at its ends where it meets the neighbours
+inline double along( double const Full, double const Atstart, double const Atend, double const Distance, double const Length ) {
+
+    auto const smooth = []( double const Share ) {
+        auto const share { std::clamp( Share, 0.0, 1.0 ) };
+        return share * share * ( 3.0 - 2.0 * share ); };
+    auto const ends { Length > 0.0 ? Atstart + ( Atend - Atstart ) * smooth( Distance / Length ) : Atstart };
+    return ends + ( Full - ends ) * std::min( smooth( Distance / fade ), smooth( ( Length - Distance ) / fade ) );
+}
+
+// distance from the joint behind the point
+inline double rail_phase( double const Along, double const Rail ) {
+
+    auto const phase { std::fmod( Along, Rail ) };
+    return phase < 0.0 ? phase + Rail : phase;
+}
+
+// share of the dip depth at a distance from the joint
+inline double dip( double const Fromjoint ) {
+
+    if( Fromjoint >= dip_reach ) {
+        return 0.0;
+    }
+    auto const height { std::cos( glm::half_pi<double>() * Fromjoint / dip_reach ) };
+    return height * height;
+}
+
+} // namespace track_uneven
diff --git a/world/TrkFoll.cpp b/world/TrkFoll.cpp
index c437553d..035e0bd9 100644
--- a/world/TrkFoll.cpp
+++ b/world/TrkFoll.cpp
@@ -267,6 +267,11 @@ bool TTrackFollower::Move(double fDistance, bool bPrimary)
     }
 };
 
+double TTrackFollower::RailPhase( double const Offset ) const {
+
+    return pCurrentTrack != nullptr ? pCurrentTrack->rail_phase( fCurrentDistance + fDirection * Offset ) : -1.0;
+}
+
 bool TTrackFollower::ComputatePosition()
 { // ustalenie współrzędnych XYZ
     if (pCurrentSegment) // o ile jest tor
diff --git a/world/TrkFoll.h b/world/TrkFoll.h
index bba97681..62f386a9 100644
--- a/world/TrkFoll.h
+++ b/world/TrkFoll.h
@@ -39,6 +39,10 @@ public:
     // inline double GetLength(vector3 p1, vector3 cp1, vector3 cp2, vector3 p2)
     //{ return pCurrentSegment->ComputeLength(p1,cp1,cp2,p2); };
     // inline double GetRadius(double L, double d);  //McZapkie-150503
+    inline glm::dvec3 UnevenBend() const {
+        return pCurrentSegment ? pCurrentSegment->uneven_bend( fCurrentDistance ) : glm::dvec3 { 0.0 }; };
+    // TTrack::rail_phase of the point Offset ahead of the axle along the vehicle
+    double RailPhase( double const Offset ) const;
     bool Init(TTrack *pTrack, TDynamicObject *NewOwner, double fDir);
 	void Reset();
     void Render(float fNr);