The ACLU of Massachusetts has three main concerns about the use of red light cameras in traffic enforcement, focusing on public safety, due process, and privacy.
The major safety rationale behind red light cameras is that they help reduce potentially dangerous side-impact crashes. Data from the Federal Highway Administration have demonstrated that red light cameras do decrease side-impact collisions by 25%--but at the expense of a 15% increase in the number of rear-impact crashes.
A study of red light cameras in Virginia commissioned by the federal Department of Transportation found an increase in total injury crashes across the state, even as it reported a decrease in crashes directly attributable to red-light running: "[A]nalysis indicated that the cameras are contributing to a definite increase in rear-end crashes, a possible decrease in angle crashes, a net decrease in injury crashes attributable to red light running, and an increase in total injury crashes." A more detailed follow-up report issued in 2007 came to similar conclusions.
Nearer to home, in 2006 the city of Swampscott conducted a rigorous public safety analysis using local data and concluded that red light cameras would not have a positive effect on local public safety.
The citations issued by red light cameras raise fundamental due process concerns. The registered owner or lessee of the motor vehicle is held liable for the alleged violation unless he or she can prove that another person was actually driving the vehicle, which very easily could be the case. How many children drive cars registered to their parents? How many spouses drive cars registered under the name of their husband or wife? Guilt is presumed over innocence.
Further hampering due process is the timing of tickets. Presently, when one receives a traffic violation, a motorist is, of course, made immediately aware of the violation by the officer who provides the ticket. With red light cameras, however, tickets may be mailed out weeks after the violation actually occurs, making a challenge to the allegation virtually impossible. And if it wasn't the registered owner/lessee driving the vehicle, that other person may not find out about the violation until even longer after it occurred. The more time in between the alleged violation and the actual ticketing, the more difficult it is to remember the circumstances surrounding the incident and to mount a defense to the ticket.
Some argue that red light camera citations are analogous to parking tickets, because neither enforcement mechanism relies on direct interaction between the driver and an officer, and the owner is liable regardless of who was driving the vehicle. As a practical matter, however, when someone borrows a car and parks it illegally, they receive the ticket upon returning to the car, and can pay the fine or otherwise take responsibility. Unlike with red light camera enforcement, there is no delay between the infraction and the citation and there is no confusion about responsibility; rather, the contemporaneous citation allows the driver to assess whether the citation was appropriate and articulate a defense.
Contrary to popular belief, the major concern about red light cameras and privacy is not about cameras taking pictures of license plates, assuming that they do not also take pictures of the drivers. Rather, it has to do with the storage by a government entity of data regarding a driver's whereabouts, whether or not the driver was issued a citation (a citation is not automatically issued simply because a photograph is taken), and whether or not those citations are successfully appealed. Such data (which includes the date and time of a particular vehicle passing a particular location) should be inaccessible to anyone for any purpose other than issuing a citation (including for other law enforcement purposes or via discovery in civil proceedings), and it should be destroyed as soon as possible.
Testimony in Opposition to Automated Traffic Control Cameras: H.917, H.918, H.1799 (PDF)
Massachusetts Joint Committee on Transportation