Speeding on motorway

Car_54

C_Mababejive wrote: »

There is far too much speeding and wrecklessness on our Mways and we really do need to have more detection and prosecution.

Wrecklessness = the absence of wrecks. Surely a good thing?

Recklessness is less desirable.

stator

Tothepoint. wrote: »

It is shall I give you a little tip on one of the ways it's done?

Next time you're on the motorway try it.

When the car in front goes under a bridge watch the back window. When it goes dark start the time.
When the second car (police vehicle) goes under the bridge the shadow will go across the windscreen onto the dash. Start the distance.
Do the same at a second bridge but stop both and you have your average speed. Or you can catch up with the car and when you are level stop the time and distance together.

Not going to be anywhere near accurate even if you've got a bright sunshiney day with a well defined shadow and enough bridges.

Tothepoint.

stator wrote: »

Not going to be anywhere near accurate even if you've got a bright sunshiney day with a well defined shadow and enough bridges.

It is and it's an accepted practice.

macman

I do hope that the OP's defence in court is not going to be the same one used here: 'I was in a rush'.

AdrianC

stator wrote: »

Not going to be anywhere near accurate even if you've got a bright sunshiney day with a well defined shadow and enough bridges.

70mph is 31.4m/s - or 400m covered in 12.7s
80mph is 36.1m/s - or 400m covered in 11.0s
Take that distance up to 1km, and the timing accuracy is much improved - 31.8s/27.7s
Take that distance up to 5km, and the timing accuracy is a doddle - 159.2s/138.5s

So Mr Stripy-Volvo follows you for three miles, and the difference between a legal 70mph and an illegal 80mph is over 20s. 97mph is 43.3m/s, or 5km in 115.5s - a whole 44sec less than the legal speed. Are you suggesting that isn't measurable from a car a short distance behind?

AdrianC

macman wrote: »

I do hope that the OP's defence in court is not going to be the same one used here: 'I was in a rush'.

...but I never, ever, ever, ever break the speed limit... Except this time, obviously. When I was damn near 40% over it.

Because to somebody who's never in their life broken the speed limit before, damn near a three-figure speed is totally indistinguishable from 70 without staring hard at the speedo, isn't it?

rich13348

stator wrote: »

It's not possible to do this from a moving car. Your perspective would mean that you can't see when the driver in front passes any particular point, like a lamppost, unless you know the distance between you and the car in front and the distance and angles between the cars and the lamppost, your perspective would make any estimates hopelessly inaccurate.

And yet it was still used by police as a way of detecting speed of the vehicle
Measure the time it take the vehicle to travel a known distance.

sheramber

AdrianC wrote: »

...but I never, ever, ever, ever break the speed limit... Except this time, obviously. When I was damn near 40% over it.

Because to somebody who's never in their life broken the speed limit before, damn near a three-figure speed is totally indistinguishable from 70 without staring hard at the speedo, isn't it?

You mean you have never been caught speeding before.

You have said you couldn't distinguish a ' near a three figure speed from 70' so how do you know that you have not done that speed before?

AdrianC

sheramber wrote: »

You mean you have never been caught speeding before.

You have said you couldn't distinguish a ' near a three figure speed from 70' so how do you know that you have not done that speed before?

Have you actually read the thread?

I don't mean that. The OP said that.

stator

AdrianC wrote: »

70mph is 31.4m/s - or 400m covered in 12.7s
80mph is 36.1m/s - or 400m covered in 11.0s
Take that distance up to 1km, and the timing accuracy is much improved - 31.8s/27.7s
Take that distance up to 5km, and the timing accuracy is a doddle - 159.2s/138.5s

So Mr Stripy-Volvo follows you for three miles, and the difference between a legal 70mph and an illegal 80mph is over 20s. 97mph is 43.3m/s, or 5km in 115.5s - a whole 44sec less than the legal speed. Are you suggesting that isn't measurable from a car a short distance behind?

If a cop car is following you for three miles he may as well match your speed and record his own, keeping the same distance. Far more accurate.