Call a meeting with the writer and director. Discuss the placement of the car chase within the plot. A poorly-placed or gratuitous car chase, even if it's done technically well, will harm the film. Elicit a shared understanding of the purpose of the car chase within the plot of the film.
Scout locations for the car chase scene. Find areas that you can get access to and block off that fit within your budget. Locations should be visibly interesting and fit in the movie. Take pictures and mark routes on a map.
Work with stunt drivers and actors to see what level of driving can be accomplished with the vehicles and talent you have available. Examine shooting locations with them to assess any possible dangers or risks.
Make a storyboard of the chase scene as it will appear on screen. Create a complete breakdown, including every type of shot necessary to achieve the desired look. Determine where each shot will take place in the scouted areas. This will save time and prevent breaks in continuity when the film is edited later.
Go to scouted locations and plan the placement of camera to get the desired shots. Doing this before shooting will save valuable time that will be limited by how long you are allowed to block off the affected streets. Determine if multiple cameras should be used to get different angles, and how to prevent crew from being seen on camera when doing their jobs. Create a rough schedule for the number of takes it requires to get the minimum number of shots and budget extra time for retakes.
Check the weather forecasts and plan around it. Rainy or icy conditions can make shooting hazardous for the drivers. If the shoot takes place over several days, make sure conditions during filming are similar. Scene that cut from overcast to sunny skies will distract viewers.