update tutorial scenario passing a crosswalk

Signed-off-by: Ericpotato <[email protected]>

docs/tutorials/ad-hoc-simulation/planning-simulation.md

@@ -218,17 +218,47 @@ To remove a traffic light from `TrafficLightPublishPanel`, click the `RESET` but
 
 [Reference video tutorials](https://drive.google.com/file/d/1bs_dX1JJ76qHk-SGvS6YF9gmekkN8fz7/view?usp=sharing)
 
-### Crosswalk stop simulation
+### Driving across a crosswalk
 
-#### Update/Reset traffic light
+When driving across a crosswalk, ego vehicle will respond to objects on the crosswalk and the traffic light. 
+
+#### Unsignalized crosswalk
+
+To pass through an unsignalized crosswalk, the ego vehicle will first slow down and stop for a safety check. Once safety is confirmed, the vehicle will proceed.
+
+1. Set an initial pose and a goal pose of the ego vehicle driving across an unsignalized crosswalk. A path will be planned.
+
+![unsignalized-placing-ego-vehicle](images/planning/passing-crosswalk/unsignalized-placing-ego-vehicle.png)
+
+2. Place a dummy pedestrian on the crosswalk and set its pose as if it is crossing the street. 
+
+![unsignalized-crosswalk-start](images/planning/passing-crosswalk/unsignalized-crosswalk-start.png)
+
+3. Engage the ego vehicle. The ego vehicle will decelerate and stop before the crosswalk. The marked **crosswalk** in the figure indicates that the stopping behavior is casued by the objects on the **crosswalk**.
+
+![unsignalized-crosswalk-stop](images/planning/passing-crosswalk/unsignalized-crosswalk-stop.png)
+
+4. Wait for about three seconds. The ego vehicle will start moving again and cross the crosswalk.
+
+![unsignalized-crosswalk-move-again](images/planning/passing-crosswalk/unsignalized-crosswalk-move-again.png)
+
+#### Signalized crosswalk
 
+1. Set the ego vehicle and a dummy pedestrian at an intersection, similar to the previous scenario. Given that the traffic light is `GREEN` by default, the ego vehicle behaves as it does at an unsignalized crosswalk, decelerating and stopping.
 
+![signalized-placing-ego-vehicle](images/planning/passing-crosswalk/signalized-placing-ego-vehicle.png)
 
+2. Delete the dummy pedestrian and set the traffic light to `RED`. The ego vehicle will decelerate and stop before the crosswalk. The marked **traffic_light** in the figure indicates that the stop is casued by the **traffic_light**. The ego vehicle will not move until the traffic light turns green.
 
+![signalized-traffic-light-stop](images/planning/passing-crosswalk/signalized-traffic-light-stop.png)
 
+3. Set a dummy pedestrian on the crosswalk agian. It can be seen that both the **traffic_light** and **crosswalk** (the two markings may overlap) affact the stopping behavior.
 
+![signalized-traffic-light-crosswalk-stop.png](images/planning/passing-crosswalk/signalized-traffic-light-crosswalk-stop.png)
 
+4. Set the traffic light to `GREEN` and engage the vehicle, the ego vehicle will stop for safety check and start move again.
 
+![signalized-passing](images/planning/passing-crosswalk/signalized-passing.png)
 
 ## Using Autoware Launch GUI