Vehicular Networks

CS 795/895

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Schedule

Blackboard

Submitting Assignments

Programming Assignment #2

Accident and Traffic Jam Analysis

Assigned: Thursday, March 6
Due: Thursday, March 27 before class

Setup the following scenario in SWANS with ASH (aka X-SWANS) extensions:

• 5 km highway
• one-way traffic
• 2 lanes
• new vehicles should enter the highway about 1 second after the previous vehicle
• maximum speed is 100 km/h
• at time 300 seconds (5 minutes), a car breaks down in the right lane 2.5 km from the beginning of the highway
• 1000 s simulated time total

• average density of traffic (vehicles/km/lane) over entire simulation
• time it takes for traffic to back up 2 km
• time that the first vehicle behind the broken vehicle (in the same lane) changes lanes and passes it (if it ever does)
• average density of traffic (vehicles/km/lane) every 30 seconds
• average speed of vehicles between 0-2.5 km every 30 seconds and average speed of vehicles between 2.5-5 km every 30 seconds

Submit: (via Blackboard and via hardcopy in class)

• Graph of average density of traffic every 30 seconds
• Graph of average speed of vehicles between 0-2.5 km and between 2.5-5 km every 30 seconds (on the same graph)
• Brief report (1-2 pages) describing how you completed the assignment and including the three required measurements (average traffic density, time for traffic to back up 2 km and time that first vehicle passes the broken vehicle)

Helpful Hints

• Modify Constants.java to setup the highway topology, vehicle max speed (in m/s), and simulation runtime.
• Look at the createSim function in the HighwayMobilitytest example to see how to control how vehicles enter the highway.
• The easiest way to obtain the needed measurements is to have each vehicle write its information to a trace file and post-process the data. To do this, in HighwayMobilityInfo.java, specify the file and write a method to output the required information to the file. This method should be called in the Next method in HighwayMobility.java. You might want to create a separate file for each vehicle.
• Causing a vehicle to break down:
  (Note: setting a vehicle's speed to 0 immediately, or even too quickly, will cause collisions, so be careful in how you setup the deceleration)
  • Determine which vehicle should break down - put a check in the Next method in HighwayMobility.java
  • Flag the vehicle as breaking down - add an attribute in HighwayMobilityInfo.java
  • Cause the chosen vehicle to stop - add code to the beginning of the Next method in HighwayMobility.java

    if (((HighwayMobilityInfo)info).isBreakingDown) {
         // this vehicle is breaking down (assuming the attribute you added is called isBreakingDown)
    
         // adjust vehicle speed according to current accel and speed
         acc = set this to some negative value and update until vehicle stops completely
         ((HighwayMobilityInfo)info).setAcceleration(acc); // set new acceleration
         initSpd = ((HighwayMobilityInfo)info).getCurrentSpeed(); // get speed
         ((HighwayMobilityInfo)info).setCurrentSpeed((HighwayMobilityInfo)info).calculateFinalSpeed(Constants.TIGGERING_DISTANCE));
    
         // set the next vehicle offset
         ((HighwayMobilityInfo)info.setOffset(((HighwayMobilityInfo)info).getOffset() + Constants.TIGGERING_DISTANCE);
    
         // calculate the time the vehicle will take to reach the new offset based on adjusted speed and acc
         sleeptime = ((HighwayMobilityInfo)info).calculateTravelTime(initSpd);
         
         // convert the highway location to 2d location
         _2dloc = convertHWLocto2DLoc(new HighwayLocation(false, LaneId, ((HighwayMobilityInfo)info).getOffset()));
    
         JistAPI.sleep(sleeptime);
         f.moveRadio(id, _2dloc);
         return;
    }