From 1f3cf4fe56ee33fe38accd7903eaee401cd2d2a7 Mon Sep 17 00:00:00 2001
From: pwarszawski <p.warszawski@gmail.com>
Date: Mon, 2 Nov 2026 16:02:06 +0100
Subject: [PATCH] AI braking: don't let the running brake test override a stop
 ahead

adjust_desired_speed_for_braking_test runs after the target speed was
worked out and overwrites AccDesired. In its third phase it holds the
deceleration near fAccThreshold until the speed has dropped by 8 km/h.
On a 20 per mille descent that application barely holds the speed, so
the phase can last minutes, and a stop signal coming up meanwhile is
ignored. In one real-time run an E186 with 19 container wagons started
the test 1290 m before a stop signal, lost 7 km/h by the signal and
overran it by 274 m after the emergency application.

While the test runs the AI now uses whichever of the two asks for the
harder braking: the test may brake harder than the route needs, never
softer.

Measured in real time, four runs of 32 consists each on a 20 per mille
descent, on the flat and on the descent with half the rail adhesion:
the test no longer runs within 600 m of a stop signal (before: down to
414 m on this branch, and 14 m with the overrun above in a build with
other brake changes), no overruns, stops 8-15 m short of the signal 86,
117 and 83 of 128 (before 90, 117 and 78).
---
 vehicle/Driver.cpp | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/vehicle/Driver.cpp b/vehicle/Driver.cpp
index 436cdb7f6..6d6c1532e 100644
--- a/vehicle/Driver.cpp
+++ b/vehicle/Driver.cpp
@@ -7927,6 +7927,10 @@ TController::adjust_desired_speed_for_braking_test() {
     if( false == AIControllFlag ) { return; } // TBD: add notification about braking test and enable it for human driver as well?
 
     auto const vel { DirectionalVel() };
+    // what the route ahead asks for; the test may brake harder than that, never softer
+    auto const routeaccdesired { AccDesired };
+    auto const routeaccdesiredgravity { fAccDesiredGravity };
+    auto const routeveldesired { VelDesired };
 
     switch( DynamicBrakeTest ) {
         case 0: {
@@ -7993,6 +7997,14 @@ TController::adjust_desired_speed_for_braking_test() {
             break;
         }
     }
+    // a stop or a restriction coming up while the test runs takes precedence
+    if( ( DynamicBrakeTest >= 1 )
+     && ( DynamicBrakeTest <= 3 )
+     && ( routeaccdesired < AccDesired ) ) {
+        AccDesired = routeaccdesired;
+        fAccDesiredGravity = routeaccdesiredgravity;
+        VelDesired = std::min( VelDesired, routeveldesired );
+    }
 }
 
 void