In the "highway-v0" scene, how can I add obstacles at a specific location?

[1cai2]

1.In the "highway-v0" scene, I want to add an obstacle at the specified coordinates, and this obstacle can appear in the observation space of ego-vehicle and does not collide with surrounding vehicles. How to realize this function?
2.In the "highway-v0" scene,the distance range of surrounding vehicles observed by ego-vehicle?
3.How can I get an observation of the nearest car in front of ego-vehicle in the current lane?

[eleurent]

1. You can add an Obstacles or a Landmark at a specific location.

https://github.com/Farama-Foundation/HighwayEnv/blob/master/highway_env/vehicle/objects.py#L214

They are both collidable, meaning they check for collisions, but only the Obstacle is solid (meaning a collision will result into a crash). So it looks like you need the Landmark.

2. This depends on your observation type. For the kinematics observation, the max distance is a constant (it should be made configuable, really)
   

   HighwayEnv/highway_env/envs/common/abstract.py

   Line 41 in f4a4989

   PERCEPTION_DISTANCE = 5.0 * Vehicle.MAX_SPEED

For the LidarObservation, it is a config:

HighwayEnv/highway_env/envs/common/observation.py

Line 677 in f4a4989

class LidarObservation(ObservationType):

3.How can I get an observation of the nearest car in front of ego-vehicle in the current lane?

There is no specific observation type for that, you'll have to implement it. You can get the nearest car in front of the ego-vehicle by calling front_vehicle, _ = env.road.neighbour_vehicles(env.vehicle), see

HighwayEnv/highway_env/road/road.py

Line 480 in f4a4989

def neighbour_vehicles(