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# Help with perceived speed of a car on a corner/bend on the road.

I've googled to hell this subject and have not found what I am looking for. i know we have some very intelligent people on HUKD so can anyone hep me with this.

There is a reason police do not set up speed cameras on bends of a road. I know of a motorist who in court argued that a police car travelling some distance behind him on a straight road could not accurately judge his speed as he was on a bend in the road and that due to some 'effect' he would appear to be travelling faster. He won his case.

He did mention some 'effect' that in science directly supported his argument, I just need to know what that is.

I have some idiot who pulled out on a roundabout on me, he says he entered the roundabout first. This means while he travelled 5ft to the impact area I travelled 75ft (from behind the white line) to the impact area in the same amount of time. That's 15 times faster than he was going. No I do not drive an F1 car.

As well as the mind boggling speed I would have had to be travelling at that point, I want to use the scientific fact about cars and perceived speed on a bend. (i.e. on the rotator of the roundabout)

HELP!

Interesting subject, the only help I can give is you travel at around 1.5 feet per second per MPH that is at 1MPH you will travel 1.5 feet (45.7cm) in 1 second. So if you traveled 75 feet in say 1 sec you were doing 112.5 mph Ummm !! thats shifting

Cos an object travelling in an arc is uniformly accelerating towards the centre?

Only thing I can think of!

:thinking:

WantOne;2855020

Cos an object travelling in an arc is uniformly accelerating towards the … Cos an object travelling in an arc is uniformly accelerating towards the centre?Only thing I can think of!:thinking:

Maybe this gives the appearence that something in an arc is going across your field of vision as opposed to away from you and so seems faster.

were did you hit cause to ht him you would have to be on r/bout 1st, if he hit you you would need to be virtualy in front of him, either way his fault

I think he's trying to get away with it, if you tel your insurance the facts and stick to them, they will see it as his fault, regardless of speed, it is his resposibility to be sure it's clear and safe to procede, what if you had been an ambulance etc, good luck :thumbsup:

They do normally give youa sheet to draw a diagramme of what happened in your eyes!! also you can get a crash investigator who knows all the physicsy stuff and can work out exatly who was travelling at what speed on impact, they can even tell if your bulbs were working if you were hit from behind!!!

and i know they horizontal stripes on the road to give the perception that you are travelling faster than you are, they make me feel sick!!! and you have to remmeber they wanna claim off your insurance so they are going to twist the truth!!

EDIT: also he is only perceiving your speed which is insumissable (or however you spell it) in a court becasue its like gossip!!!!

Its pointless getting into a debate with the person you crashed into, let the police and insurers decide... (whatever your or their opinion is irrelevant anyway as you both are denying responsibility). FWIW it sounds like they pulled out without giving way thus they are at fault, but that is a concern of the insurers and police, not you....

Best of luck, be prepared there is a decent chance that 'fault' won't be decided and you will both claim of your own insurers - but its pointless getting too worked up about it as its beyond your control anyway...

Banned

jah128;2855310

Its pointless getting into a debate with the person you crashed into, let … Its pointless getting into a debate with the person you crashed into, let the police and insurers decide... (whatever your or their opinion is irrelevant anyway as you both are denying responsibility). FWIW it sounds like they pulled out without giving way thus they are at fault, but that is a concern of the insurers and police, not you....

Nothing to do with the police unless someone was injured

jah128;2855310

Its pointless getting into a debate with the person you crashed into, let … Its pointless getting into a debate with the person you crashed into, let the police and insurers decide... (whatever your or their opinion is irrelevant anyway as you both are denying responsibility). FWIW it sounds like they pulled out without giving way thus they are at fault, but that is a concern of the insurers and police, not you....

Quite agree, had a prob with someone who thought I was the cause of his accident, he hit someone else in the rear (to close duh !! ) So I let Insurance co know and they just explained to him it was his own fault,

csiman;2855378

Nothing to do with the police unless someone was injured

It is if they consider someone to have been dangerous driving, although it doesn't sound like that is the case here :thumbsup:

All depends on the speed you were travelling, not the speed you crashed at as that will be much slower as you would have used your brakes.

The only way this can be determined is by eye witnesses.

Benjimoron;2855398

All depends on the speed you were travelling, not the speed you crashed … All depends on the speed you were travelling, not the speed you crashed at as that will be much slower as you would have used your brakes.The only way this can be determined is by eye witnesses.

Not true im afraid, what one person considers to be fast another person wouldn't, its just an oppinion on the speed which has no backing evidence,

The only way to determine the speed is for a crash investigator to mark up the road and reconstruct the accident! :thumbsup:

foxymissroxy;2855420

Not true im afraid, what one person considers to be fast another person … Not true im afraid, what one person considers to be fast another person wouldn't, its just an oppinion on the speed which has no backing evidence, The only way to determine the speed is for a crash investigator to mark up the road and reconstruct the accident! :thumbsup:

From what info, people's opinions of the events???

I haven't heard of this 'effect' on corners before, my take is simply that if you put a speed camera on a corner it can't cover much of the road. If you think about it, putting a speed camera on a straight piece of road will allow it to cover a reasonable section of the road as the camera is sitting parallel to the road. However if you put one on a corner, the camera and road are only parallel at the point where the camera is as the road curves away leaving the camera pointing to the side of the road.

Similarly when a police car is following a car down a straight section of road if it is measuring the speed of the car in front the signal is going to go straight forward and straight back. However on a corner the target car is going to be at an angle to the police car which means the signal is going to bounce at an angle and the police car will only receive a portion of the signal back. However I would have thought if the police car is showing a higher speed limit and the gap to the car in front is not visibly reducing then it's clear the car in front is speeding. In the case you've mentioned the target car sounds like it was too far ahead to visibly estimate the relative speed.

The only perceived speed difference I can think of is that the car is obviously pushing you sideways and backwards whereas straightline acceleration only pushes you backwards. As others have mentioned you will just have to describe what happened to your insurance company and let them settle the blame, aside from your car quantum tunnelling I don't think there is any strange physics reason for it.

John