Right I'm sure we all know that the above they are a fixed mesure of speed and distance, but how much speed is each marking equivelant to??

 

Where would I find this info out?

 

Anyone got any info as MOT people I've spoken to don't seem to know how much speed each Mark mesures and the Crown prosecution tell me to speek to the MOT even though they are relying on this information to procecute people.

 

I always thought that each mark was 1 mile an hour as there are 30 marks and anything exceeding the speed limit by 30mph is an instant ban.

All on here

 

http://www.abd.org.uk/gatso_photo_checking.htm

 

 

O-level maths required!

All on here

 

http://www.abd.org.uk/gatso_photo_checking.htm

 

 

O-level maths required!

 

Cheers thats grate, But being a mathmatics dumb ass I don't understand how to apply the formula.

Tell me what you want to know and I'll have a go at working it out if you want.

Cheers but I'd also like to understand how to apply the formula than if needs bee I can argue her case yet again.

 

Picture shows the car halfway between the 3rd and 4th mark on the road. The markings are spaced at 5ft which means she has traveled roughly 12.5 to 13 ft in 0.5 seconds.

Oh yes they are claiming the car is traveling at 36mph

Hmmmm.... according to that formula the car was doing 23.9mph

 

3.5 (marks) X 5 (feet between marks) X 0.6818 (converts feet per second to mph)

--------------------------------------------- = 23.863mph

0.5 (seconds)

 

 

Maybe it's wrong or the marks weren't five feet apart.

 

Or maybe the police are trying it on?

 

Where's Shrimpy when you need him - he's good at maths!

that formula is wrong. if you go past 8 marks useing that formula you are doing 5mph.

 

First count the number of lines the vehicle has travelled in the time between the first and second frames (0.5 seconds). the distance between each line is 5 feet.

 

Number of lines travelled 3.5

 

Multiply by the distance beteen each line 5. (=17.5)

 

The result is multiplied by 2 to give the speed of the vehicle per second= 35

 

To convert this to mph = 35 (feet per second) multiplied by 3600 (seconds per hour) divided by 5280 (feet per mile) = 23.83mph

Er.. 8 x 5 x 0.6818 / 0.5 = 54.544.

 

Gonna have to agree with Craig here, sounds like that 36 mph is BS

that formula is wrong. if you go past 8 marks useing that formula you are doing 5mph.

 

If you went past 8 marks between photo 1 and photo 2 and the time difference between photos was say 0.5 seconds and the distance between marks was 5 Ft then you would have been doing 54.54MPH

 

[8(Marks) * 5(feet between marks) * 0.6818 (Miles-Ft conversion)]/0.5 (time)

 

= 54.54

The 36 mph does sound like BS if the marks are 5 feet apart and the interval between the photos was half a second.

 

Edit - according the the ADB site the camera judges the speed with radar too but this can be wrong and the photos are generally considered more reliable.

 

 

Edit II - eight marks would be 54.54mph

I understand the math. the formula is not correct though.

I understand the math. the formula is not correct though.

 

Based on the figures you have both the formula using the 0.6818 and the long way round you did it both give 23.8 MPH..

I worked it out to 23.86 mph too but using a different method:

 

3.5 x 2 x 5 = 35fps (3.5 marks x 2 half seconds x 5 feet per unit)

 

35 x 60 x 60 = 126000 fph (35 fps x 60 seconds x 60 minutes)

 

divide by 5280 (feet in a mile) = 23.86 mph

 

If the distances between the markings are correct then there was no speeding involved. At 36 mph you would have to cross 5.28 marks.

 

HTH Colin

 

Edit: took me so long to work out, didn't notice the same conclusion above :bow:

The marks would have to be 7.5 ft apart to be doing 36 mph. Might be worthwhile going to the spot and measuring them. If they are 5 ft apart get a solicitor involved and prove them wrong.

If I was you I would write back and ask for the spec of the camera. The time delay between photos, the distance they think the lines are and the formula they are using.

 

can you scan the photos so we can see the car on the lines.

The marks would have to be 7.5 ft apart to be doing 36 mph. Might be worthwhile going to the spot and measuring them. If they are 5 ft apart get a solicitor involved and prove them wrong.

 

That would mean the Gen 7 Celica is roughly 22.5 ft long and it certainly isn't. It a dam sight shorter than the Zed and thats only 14.5 ft long.

That would mean the Gen 7 Celica is roughly 22.5 ft long and it certainly isn't. It a dam sight shorter than the Zed and thats only 14.5 ft long.

 

 

The road markings have to be 5 feet appart as the law says thats how they measure it.

However the speeds are comming back wrong, whatever way you work it out yoour under the speed. I would contest this and make them acountable for any fees you incure. A nice letter explaining why you dont agree and ask them for calibration proof should be all you need.

Try looking at these 2 sites, if you have any questions about motoring law these are the sites to go to.

 

http://www.pepipoo.com

http://www.safespeed.org.uk