Engine immobilizer

The goal here is to give the police the ability to bring a “fleeing” car to a dead stop, electronically.

I’m led to believe the only way to do this is to emit an EMP burst, effectively frying the cars onboard electronics.

Is this really the only way?

Perhaps this device could be mounted on strips to be laid out across the road in front of the vehicle, as with the row of spikes currently being used.

Or alternatively, these “transmitters” could be located roadside or even embedded in the roads surface at regular distances,much like "cats eyes".

Thoughts people.

I think there is some misunderstanding about the likely EMP characteristics required to achieve this objective.
Remember that the military will be more concerned about this than civilian Police.
The ability to stop armoured vehicles with judiciously buried/positioned devices is of obvious interest.
In fact nuclear explosions are known to create EMP of the necessary strength, & very active sunspots also disrupt communications but are probably unlikely to fry electronic vehicle controls.
In short you would need a very powerful source; & to prevent local damage beyond the target area, that source would need to be very close to the electronics which are already noise ruggedised.
This is just not going to happen with today's technology.

If you have a US or european aproved car alarm build in your car it is already there.
By LAW all these systems can remotely controlled by LAW enforcement and others.

I agree with everything Peter said. The challenges are significant. The research, in some cases classified. I can tell you first hand that many military aircraft are built to minimize the effects EMP. The actual equipment is large and requires a very large power source. Here's a video (Future Weapons) that shows a working research example, notice the size of the equipment. http://www.youtube.com/watch?v=0odJKYTzXg8
One thing I will disagree with the video is that they state a nuclear powered EMP at 300 miles above the earth could disable the whole USA. While that may be theoretically possible the power required to do that, I believe that is a gross exaggeration of what is practical.
I do love the idea of an old beater truck rolling down the road while the shiny new cars line the shoulders with their brains fried.

The GM cars have the Onstar system on them and Police just need to contact Onstar and give them the VIN number and they can kill it. It is cell phone based and a digital command is all that's required. Now hack that system and you might be able to send bad drivers to the edge of the road and have a clear drive to work. Since GM has it I'm sure the other manufacturers have something similar.

Since we are on this topic I will also mention the fact that the memory in your car keeps things like speed, braking, gear selection, etc. It has been used in a court case that a person near here was killed in to prove that the driver was running over 100 mph.

We also have traffic cams on every major overpass in the city. They haven't acknowledged it yet but it is possible that they are using license plate recognition software to track movements.

Big Brother is alive and well and he is going to nab a lot of ignorant bad people in the coming years.

See, that's what I'm talking about. How does this work?
EMP is clearly the wrong way to go.

The police transmit to the alarm system with a special code to turn of the ignition system.

the local coastal radar listening station has a habbit of killing vauxhall cars. the local car repairers has now become a specialist repairer.........the forces maintain they arent to blame, but its strange that over a hundred cars a year break down in the same spot with the same fault ...?? do-de-da-da (my lame imitation of x-files tune LOL )

on a more relavent note, there was a video shown on tv several years back of a police car with a harpoon that administered a EMP. the harpoon was like a fixed battering ram, and the police could then disrupt the engine systems. if i find it on youtube i will post

Here's one YouTube "contribution".
http://www.youtube.com/watch?v=j8f-RtwqVY4
Not very convincing IMHO but this info has come from somewhere.

Police have to be concerned about safety, frying cars computer can have unpredictable results like breaks blocking up resulting in a crash, so no, EMP is probably not the answer here

...and the device has to already be installed in the vehicle you want to disable.

Back in the '80s (or '90s don't remember for sure), there was a stretch of the 405, in Van Nuys, CA where the rear windshield washer on my Dodge Caravan would come on, all by itself -- the wipers and the washer fluid pump would come on and could only be turned off by killing the ignition. It happened every time I drove, Northbound, through that area. Not Southbound--only Northbound.

Visible from the Southbound side was the Anheuser Bush brewing plant. From the Northbound side was an industrial looking building with a yard full of radar antennas!