Differential speed when passing on motorways etc
Discussion
I have noticed on the roads that there seem to be two schools of thought regarding the differential speed between the overtaking car and overtaken car on dual carrige ways and motorways. Some people accelerate hard when overtaking cars, and others slow down to 0.1 mph.
Please note I am not talking about outside/middle lane hogging or elephant racing, or overtaking on single lane B roads: for this discussion we are assuming you are not a numpty and your cars capabilites allow you to choose the speed you are travelling.
When passing a car or lorry on dual carriage way.
If you go very slowly, you spend more time in an overlap , therefore you are more likely to be affected by either a deliberate lane change, a sudden swerve to avoid another car/debris, or a forced change like a windblown lorry. You also spend more time in the blindspot of the car. Your options are also limited to braking, as your car inertias will be too high to accelerate out of trouble.
If you are going too fast, you will be unable to brake/swerve to avoid such an event if it happens in front of you.
So it seems to me that there can be too fast and too slow, what do PH'ers think is a happy medium ? Does the speed limit affect your behaviour when passing ?
Please note I am not talking about outside/middle lane hogging or elephant racing, or overtaking on single lane B roads: for this discussion we are assuming you are not a numpty and your cars capabilites allow you to choose the speed you are travelling.
When passing a car or lorry on dual carriage way.
If you go very slowly, you spend more time in an overlap , therefore you are more likely to be affected by either a deliberate lane change, a sudden swerve to avoid another car/debris, or a forced change like a windblown lorry. You also spend more time in the blindspot of the car. Your options are also limited to braking, as your car inertias will be too high to accelerate out of trouble.
If you are going too fast, you will be unable to brake/swerve to avoid such an event if it happens in front of you.
So it seems to me that there can be too fast and too slow, what do PH'ers think is a happy medium ? Does the speed limit affect your behaviour when passing ?
Well it does if Numptie in front is driving a few mph under the SL - means I have to exceed SL to get safely past him/her and leave reasonable clearance to get back in without carving said numptie up!
And if you can't accelerate pass him/her, there's really no point in creeping pass over the next 3/4s of a mile or so - you might as well stay where you are until you can pass safely and without exceeding the SL.
Actually I get told off by SWMBO if I go over the limit because I'm on a clear road (apart from me and Numptie)and Numptie in front is dead set on doing 2/4 mph below, according to my speedo, the SL.
David
I'm sure I know what I'm mean to type!
And if you can't accelerate pass him/her, there's really no point in creeping pass over the next 3/4s of a mile or so - you might as well stay where you are until you can pass safely and without exceeding the SL.
Actually I get told off by SWMBO if I go over the limit because I'm on a clear road (apart from me and Numptie)and Numptie in front is dead set on doing 2/4 mph below, according to my speedo, the SL.
David
I'm sure I know what I'm mean to type!
ohopkins said:
Please note I am not talking about outside/middle lane hogging or elephant racing, or overtaking on single lane B roads: for this discussion we are assuming you are not a numpty and your cars capabilites allow you to choose the speed you are travelling.
When passing a car or lorry on dual carriageway.
8< 8< snip snip
So it seems to me that there can be too fast and too slow, what do PH'ers think is a happy medium ? Does the speed limit affect your behaviour when passing ?
The answer is like the length of the proverbial piece of string, it all depends.
A) Take example unlimited German autobahn to remove the speed limit issue.
Then it depends upon lane separation and how stable they look.
A1) If in next lane to overtaken vehicle probably limit the differential speed to about 20 mph, increased to 30 if I'm happy they are going to stay where they are.
A2) If possible make a complete clear lane between them and me (ie them in 1 me in 3+) and just nail it.
B) Now in the situation where there is a limit entirely different matter and does depend to a very large extent on how sure one can be that electronic / biological enforcement is not in place.
Answer to that in detail will take too long, but if their speed is such that approach A1 is possible without going over the limit then OK. Otherwise keep to limit, maybe plus a few mph. The opportunity for A2) on our god forsaken road network is almost non existent these days especially for the points free conscience.
FiF
medicineman said:
IAM teaches to always look for "escape routes" if anything happens. So if you are along side another car or truck your escape is cut down, so I would say as fast as is sensible.
Quite so. That's why low speed limits create danger.
I was around pre NSL. It was predicted that 70 would create bunching. It was noticeable that bunching started when the limit was imposed.
We should be allowed to pass as fast as possible to minimise risk whist overtaking on single carriageways.
deeen said:
I try to keep the differential down to no more than 30 mph when passing on a dual carrigeway. On single carrigeway, I prefer to accelerate by hard to minimise time on wrong side of road.
way back.... I found that a diffential of 80 leptons caused a backwash effect of the over-takee driving into the kerb. However if the differential were to be 120 leptons or more, they didn't even notice. So I guess the ideal speed difference is less than 10 leptons, or greater than 100 leptons. I trust this helps.
Of course I am talking about my private racetrack.
Stay safe!
My 30 is to give ME a chance when they pull out in front of me! You know... ("Oh no theres a lorry a mile in front of me and an orange car a mile behind me comong up fast so i'd better pull into the outside lane NOW in case he is coming past me when I want to go past the lorry and then I might be boxed in or wake up or something and then and then and... what was that orange thing that just went by on the inside?")
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