Based on the scenario at the beginning of this article, let's assume that you do suspect you have located a car bomb. Now what? Using the military guidelines having proved themselves in Iraq, FOLLOW THE 4 C's!
Clear - Leave the immediate area and expect an imminent detonation.
Cordon - Establish safe evacuation distances and be familiar with the Bureau of Alcohol Tobacco and Firearms Explosives Standards (linked below) to know how far to place your barriers at a minimum.
Control - Using binoculars from a safe distance, maintain visual surveillance of the vehicle to ensure security of the scene remains unchanged.
Call - Your local bomb squad. As the first responder your job is the immediate protection of lives and securing the scene, until specialist assets arrive to render the location safe.
All the training and knowledge accumulation in the world will not keep you or your community safe if you or your agency suffers from the it won't happen here mindset. Threat recognition begins with realization leading to actualization. First responders (Police, Private and Corporate Security, Fire and EMS) have always been and will continue to be at the anti-terrorism tip of the spear. It's time we started acting like it.