correct slight overshooting. investigate a bus reaching a stop with

non-zero speed

docs/project/references.md

@@ -20,6 +20,7 @@
 - http://www.seattle.gov/seattle-pedestrian-advisory-board
 - Socrata
 - http://transportationcamp.org/
+- https://www.seattle.gov/transportation/projects-and-programs/programs/neighborhood-street-fund / https://www.seattle.gov/neighborhoods/programs-and-services/your-voice-your-choice
 
 ## Similar projects
 

sim/src/driving.rs

@@ -375,7 +375,16 @@ impl Car {
             Some(Intent::StopAt(lane, dist)) => {
                 if self.on == Traversable::Lane(lane) {
                     if self.dist_along > dist {
-                        panic!("{} overshot! Wanted to stop at {} along {}, but at {}. Speed is {}. This last step, they chose {}, with their max being {}, and consequently traveled {}", self.id, dist, lane, self.dist_along, self.speed, accel, self.vehicle.max_deaccel, dist_traveled);
+                        // But be generous, maybe.
+                        if self.dist_along - dist <= EPSILON_DIST && self.speed.is_zero(TIMESTEP) {
+                            error!(
+                                "{} overshot just a little bit on {}, so being generous.",
+                                self.id, lane
+                            );
+                            self.dist_along = dist;
+                        } else {
+                            panic!("{} overshot! Wanted to stop at {} along {}, but at {}. Speed is {}. This last step, they chose {}, with their max being {}, and consequently traveled {}", self.id, dist, lane, self.dist_along, self.speed, accel, self.vehicle.max_deaccel, dist_traveled);
+                        }
                     }
                     if self.dist_along == dist && !self.speed.is_zero(TIMESTEP) {
                         panic!("{} stopped right where they want to, but with a final speed of {}. This last step, they chose {}, with their max being {}", self.id, self.speed, accel, self.vehicle.max_deaccel);

sim/src/kinematics.rs

@@ -308,7 +308,7 @@ pub fn results_of_accel_for_one_tick(
     assert_ge!(dist, Distance::ZERO);
     let new_speed = initial_speed + (accel * actual_time);
     // Deal with floating point imprecision.
-    if new_speed < Speed::ZERO && new_speed.is_zero(TIMESTEP) {
+    if new_speed.is_zero(TIMESTEP) {
         (dist, Speed::ZERO)
     } else {
         assert_ge!(new_speed, Speed::ZERO);

sim/src/transit.rs

@@ -4,7 +4,7 @@ use crate::spawn::Spawner;
 use crate::trips::TripManager;
 use crate::view::AgentView;
 use crate::walking::WalkingSimState;
-use crate::{CarID, PedestrianID, Tick};
+use crate::{CarID, PedestrianID, Tick, TIMESTEP};
 use abstutil::{deserialize_btreemap, serialize_btreemap};
 use geom::{Distance, Duration};
 use map_model::{BusRoute, BusRouteID, BusStop, LaneID, Map, Path, PathRequest, Pathfinder};
@@ -141,6 +141,12 @@ impl TransitSimState {
                 let stop = &route.stops[stop_idx];
                 assert_eq!(stop.driving_pos.lane(), view.on.as_lane());
                 if stop.driving_pos.dist_along() == view.dist_along {
+                    if !view.speed.is_zero(TIMESTEP) {
+                        panic!(
+                            "{} arrived at stop {}, but speed is {}",
+                            car, stop.id, view.speed
+                        );
+                    }
                     // TODO constant for stop time
                     self.buses.get_mut(&car).unwrap().state =
                         BusState::AtStop(stop_idx, time + Duration::seconds(10.0));
@@ -157,6 +163,16 @@ impl TransitSimState {
             BusState::AtStop(stop_idx, wait_until) => {
                 let stop = &route.stops[stop_idx];
                 assert_eq!(stop.driving_pos.lane(), view.on.as_lane());
+                if stop.driving_pos.dist_along() != view.dist_along {
+                    panic!(
+                        "{} stopped at {}, but dist_along is {}, not {}. Speed is {}",
+                        car,
+                        stop.id,
+                        view.dist_along,
+                        stop.driving_pos.dist_along(),
+                        view.speed
+                    );
+                }
                 assert_eq!(stop.driving_pos.dist_along(), view.dist_along);
 
                 if time == wait_until {