Getting Started With Traffic Simulation in JavaScript

Question

I am going to be asking a lot of questions in the upcoming months. For my ninth grade science fair project I would like to create a traffic simulator in order to test whether or not interconnected communicating traffic lights can increase traffic flow. I have a couple of generic questions that I need help with...

• How would I represent roads?
• How would I make car follow a road?
• How would I make a car switch lanes or roads?

I am not looking for specific code, just good pointers and resources to help me get started. Any help is appreciated, C.Ruhl.

PS I am only in high school so no advanced math notations please :)

Answer 1

One possible approach which is taken quite often is to use a discrete model for roads and cars' positions.

Each position on the road can either be occupied by a car (blue dot) or be empty. Cars move at discrete time steps by exactly one position (if the target position is empty) along the given arrows. Thus a car can even switch lanes if it would otherwise have to slow down or stop.

You can further improve it by using separate timesteps per car (simulating faster/slower cars) or in many other ways.

After you've defined your roads (i.e. the positions and their follow-up positions) by an appropriate data structure this model is relatively easy to simulate but already shows interesting effects.

Answer 2

1. Forget about the UI.
2. Represent each object in its base form --only put object properties in it. Example, a car will have a size and ability to move. But it won't have the logic to make it move. Similarly a traffic light will have states such as green, amber and red. But it won't have the logic to switch between these states. Similar classes for roads, lanes etc.
3. Build a different class for the driver. This class will contain all methods such as lane shifting, stopping, turning, moving forward etc. More technically, this will be your "actor" and will act on the veichle. A similar actor would be for traffic light control which will act on a network of traffic lights. Make it an interface and have two implementations to it --one that takes advantage of interconnectedness and other that operates on static times.
4. Optional add a UI on top of this object model. Don't go fancy, have simple dots to begin with. Once you get all simple stuff working, adding more fancy features should be easy and impact free (relatively).

This will be a very challenging project.

But if your objective is a proof of concept, I have a simpler suggestion. You can go user generated here and get all the complexity of simulation out and all the accuracy in. Start with 15-20 remote controlled cars, a cardboard model of a fictional town, some bulbs to simulate traffic lights and some volunteers who know how to drive. Have a preprogrammed sequence of on and offs written on paper and assign some of the volunteers to control those lights. Have another set of volunteers control the cars. If you have hands on experience in basic electronics you can build a timer controlled circuit to control the lights.

All the very best!

Answer 3

You could try the SIM.JS discrete event simulation library in Javascript. They have a very simple example for traffic at road intersection simulation here.

Answer 4

Ooh, Conner, you've found an interesting question indeed -- and one which is the subject of research even today. Here's a suggestion: before you fret about how to do it in JavaScript, spend some time thinking just how to do it at all.

Here's a suggestion: think about the objects invovled first. You have Cars, and they travel along Roads. Start with a square grid of roads, so your cars go from intersection to intersection.

Pick a fixed speed for the cars, so it takes a constant time to travel from intersection to intersection.

Each intersection has a traffic light, which can be red or green. If it's red, of course cars can't go through; they have to wait.

Now, your basic program will look like

time = 0
while time < end-time:
    for each car:
        update the car's location
    add time consumed to time

when you update the cars location, what happens? (Hint: the car moves; can it go through an intersection or not?)

That will give you a start.

Answer 5

For my Bachelor's degree exam I developed a traffic control web-app that tracked the vehicles in my town in real-time and I used google maps api.
I suggest you use a map service such as maps.google.com , yahoo.maps.com...
They have an api for everything... you can use markers to represent anything on the map (cars,street lights,even pedestrians :)) ) and you can use their api to calculate distances and paths.
It may seem a bit more complex then the average div-implementation, but, trust me, it's a big plus to use a service with a well-organised api.
+it would have a more professional look ;).