I witnessed an unusual traffic accident yesterday: what began as a typical rear-ending took a bizarre turn when the 'rear-ender' reversed at high-speed and rammed the 'rear-endee' again!
As I navigated the Ottawa Police Web-site later in the day, their instructions for submitting traffic complaints got me thinking about my driver rating system idea again: specifically, note how much information is required regarding the timing, the other driver, their vehicle, etc. Now, admittedly, I glossed over how a particular identifier would be represented as one of many potential vehicles in proximity with you, but, setting that aside for the moment, a lot of the information the police are looking for could be automatically generated; the process would also be more timely, and possibly even safer, if you compare it with the scenario where a person is trying to relay all that information over a handheld cell-phone while driving.
On the point of representing particular identifiers on a person's appliance, the balance between the cost and complexity (and safety) is at the crux of the problem: ideally, the system would visually represent the makes, models and positions involved, updating the information every few seconds, on a sizable screen that can be centrally located in the vehicle's dash. However, at a minimum, a multi-line text display of license plate number, make, model, colour and direction (with respect to your vehicle: so, front, back, left, right, etc.), updated regularly, would suffice. (You wouldn't want to rely on the license plate alone, since the vehicle could be screaming through an intersection on a path perpendicular to yours; also, straining to read a plate in your rearview mirror could be a serious distraction.)
One final point on the subject of this system being a target: all the contact information that the police require from the person reporting the incident shouldn't be included in this system. Depending on how drivers are issued their RFID tag and associated identifier, the DMV system or a separate system could be queried by police using the reporting appliance's identifier. That way, people who want to know the address of everyone who drives down their street need access to more than this system.