Can You Be Charged This Way?

Most modern cars have extensive memory in the engine control computers-can you be charged with speeding, if the police were to interrogate your vehicle’s computer (and find that the car had been driven at speeds over 65 MPH?). Would such a charge hold up in court?
I’ve always wonderd why toll roads don’t do this-your ticket is timestamped at entry onto the road-if you exit at a time (that indicates you have exceeded the legal speed limit0, should you be assessed a fine?

I was unaware of consumer car ECMs storing such data… your airbag controller on the other hand records various parameters when triggered, including vehicle speed. There have been a few occasions of that information being used against a driver in court.

Because toll roads are about generating revenue, and if everyone who sped on them got fined, they’d stop taking the toll road.

I don’t think the computers normally in a car would be able to give enough information to do this.

A few years back a rental car company used the GPS recievers in the car to track customers and fined them if they had been speeding.

They dropped this practice very quickly after a lot of consumer backlash.

Does proof that the vehicle was moving at a high speed, by itself, constitute a violation? Can’t you drive as fast as you want on a race track, or on your own private property?

Taking the OP at face value: assume that the car’s computer records information about the speed of the vehicle. Assume that an examination of the computer reveals that the car has been driven at speeds over 65 MPH at various points in time. Would those electronic records be sufficient to support a charge of speeding?

Answer: standing alone, no. The police must first prove who the driver is. Outside of David Hasselhoff and the way-brighter-than-him car KITT, cars don’t go on their own. So someone was driving that car. Maybe you, maybe someone else. The burden is on the police to prove it was you. Imagine the resources they’d have to put in to establish evidence that you were the driver. Is that worth their time? Probably not.

I’m leaving out the other issue: that they’d have to prove that at the time you exceeded 65, you exceeded the speed limit (i.e., you weren’t somewhere where such a speed is legal).

Also, remember that the police need probable cause to support a warrant. Which means they need some basis other than a fishing expedition to support a request to see your car’s computer.

Having said that, though, I could see how this could be an awesome tool for the police. If everyone believed that the cops could tell from your computer that you’d violated the vehicle code, maybe everyone would drive more safely.

These tools are called Event Data Recorders. (EDRs).
Here is a summary of legislation about EDRs
So what can an EDR record? By federal mandate the Engine Control Module must capture certain engine running parameters at the instant of a fault be recorded. Coolant temp, engine RPM I know are captured, there may be a few others like gear position and throttle position, but off the top of my head I don’t recall. A car maker may choose to record additional parameters above the ones required to assist the technicians in repairing the car. To the best of my knowledge nobody has an ECM that makes a continuous recording of parameters (like an airliner’s black box)
SRS (airbag) systems may record several parameters starting several seconds before an airbag deployment. These may include, deceleration rate, vehicle speed, seat belt usage. Note that these parameters are only saved in the unit after an airbag deployment.
Other systems in the car may have EDRs and store parameters at the point of fault. These parameters are directly related to the fault and system involved. A climate system fault might for instance record A/C compressor condition, fan speed, and engine temp.
Here is a position paper from GM on EDRs. This pretty much mirrors Volvo’s position (BTW EDR existence is disclosed in Volvo’s owner’s manuals. This is due to California law.)
As far as their accessibility goes, at least in California the car company cannot access it for use in court unless the car owner agrees. (note the owner may not be the driver involved in the case.)
In California it takes a court order to allow the police to download an EDR.
Bottom, line, don’t panic that you will get a speeding ticket in the mail next week for what you did this AM on the way to work. I also know of no cases where a warranty claim has been denied on the basis of EDR info.

Here is a recent article about it:

I don’t know that anyone’s ever been assessed a fine based on their calculated speed from a Thruway ticket. My old boss while I was working for a regional company that did a lot of travelling work told of one day when she got to an Thruway exit about a half hour before she could have gottten there legally, and was given the choice to pull over and wait that half hour in the parking lot there, or they’d call a Statey to give her that ticket.

I don’t know that’s what happened, but it’s what I was told it happened. And the way she drove I could believe it of her.

Here in the Netherlands they have some brand spanking new technology to make sure nobody speeds on certain parts of our roads.
The system takes a photo of your numberplate and stores it when you enter a certain part of the road and another one when you leave.
It then compares the time and distance and presto : instant ticket sent to the owner of the car.
The only way to circumvent it would be to make your licenseplate unreadable, which is considered a felony.
The only problem is when somebody borrows your car and speeds in those areas.
I am not sure how they handle somebody objecting to the fine, because they weren’t the driver.

The question is whether Insurance Companies can get their hands on the EDR data after an accident - as they become more common and record more data, it would not surprise me if policies require access to the data - thus claims can be examined (and rejected) more easily.


Depends on where you are. In California it takes a court order, or the approval of the car owner. See the first link in my post above.

Off to GQ.

I have two FOAF stories, both about the Ohio Turnpike (I-80), that have similar subject matter. I also remember this example being used to vividly illustrate the Mean Value Theorem in calculus, though, and I wonder if the FOAF stories are not just an offshoot of dozens of calculus professors’ imaginations.

The method is definitely used over shorter stretches of ground; speed enforcement from aircraft relies on a stopwatch and pre-surveyed lines painted across the highway. It goes by the name VASCAR and every description I’ve seen calls it a “system” with a “computer” but a stopwatch and a calculator would do the trick just fine.

But isn’t this exactly what they do with red light cameras? They send the citation to the owner of the vehicle, with no regard for who was driving it.

The difference is with a red light camera you are being charged by something that is visible to anyone who happened to be at that intersection at that time.
The worry is with an EDR is that your car might contradict your testimony in a legal case and cause you to lose the case. Kind of a self incrimination, if you will.
You: I was traveling 35 mph the speed limit when the accident occurred, and I was braking as soon as I saw the other car.
EDR: The car was going 75 and the brakes were not applied when the airbags deployed.