vehicle.js

// using the "Vehicle" API

// a vehicle can be created from an arbitrary position / heading if you like
position = {
  coords: {
    longitude: -71.00000
    latitude:  42.00000
    heading:   78
  }
}

var v = new Vehicle(position);

// you can init the vehicle from the current postion as returned 
// by geolocation, but you have to put all of your logic in the 
// callback
initVehicleFromGeoLocation(function(vehicle) {

  // do what you want with 'vehicle' here

  },
  function(msg) { /* i'm called on error */ },
  function()    { /* i'm called if geolocation is not supported */ }
);

// once you have a vehicle you can view it's properties
vehicle.latitude
vehicle.longitude
vehicle.heading.heading   // 87 degrees
vehicle.heading.direction // enum value for East (3)

vehicle.heading.toString(); // shows "E" for east
vehicle.toString();         // shows "vehicle: { latitude ... "

// there are a few helpers too
vehicle.sideOfVehicle(position) /* will tell you if the passed position 
                                   is on the Left or Right of your vehicle */

vehicle.sideOfEvens(function(side) {
  // Left is 0 and Right is 1, so
  alert("even numbered addresses are on the " + (side ? "right" : "left"));
}); /* for street cleaning queries */