What's your stopping distance at 50mph?
Discussion
I found this interesting: http://www.reghardware.com/2012/05/28/volvo_tests_...
The Highway Code says 38m braking (not inc. thinking) distance at 50mph, and as we're often told, that's based on something like a drum braked Ford Anglia.
In 2001, the AA reckoned that my car had a minimum 26m stopping distance at 50mph, under sudden braking with a 22kg pedal load. I would consider myself very lucky to be able to reproduce that, but I've never tried in earnest. It feels rather more like you might plan such an event on a calendar. Or globe.
Have you ever got close (deliberately or otherwise) to figuring out just what the limit of your car is, and has it affected your driving?
story said:
Three cars have successfully driven themselves by automatically following a lorry for 125 miles on a public motorway in the presence of other, normal road users.
...
The 125-mile test run was conducted at an average speed of just over 50mph and kept the three cars behind the truck at an average separation of 6m.
Now obviously there are reasons for that (e.g. stop people merging between cars) but it got me thinking about stopping distances....
The 125-mile test run was conducted at an average speed of just over 50mph and kept the three cars behind the truck at an average separation of 6m.
The Highway Code says 38m braking (not inc. thinking) distance at 50mph, and as we're often told, that's based on something like a drum braked Ford Anglia.
In 2001, the AA reckoned that my car had a minimum 26m stopping distance at 50mph, under sudden braking with a 22kg pedal load. I would consider myself very lucky to be able to reproduce that, but I've never tried in earnest. It feels rather more like you might plan such an event on a calendar. Or globe.
Have you ever got close (deliberately or otherwise) to figuring out just what the limit of your car is, and has it affected your driving?
Article said:
On-board cameras, radar and laser tracking allow each vehicle to monitor the one in front. Wirelessly streamed data from the lead vehicle tells each car when to accelerate, break and turn, all in real-world traffic conditions.
File this mob with the rest of the "didn't pass the PH spelling test so any points made are invalid" files.
trashbat said:
Have you ever got close (deliberately or otherwise) to figuring out just what the limit of your car is, and has it affected your driving?
I have, lots, specifically to learn the limits. I've done it in a variety of conditions on a variety of surfaces. Every winter if there's a clear stretch of road and it's safe to do so I'll test the limits of traction so I know what the limits are [/]in that car, in those conditions[/] - this used to mean locking up or spinning the wheels, but now involves squeezing the stop or go pedals till the systems kick in. I've induced understeer and oversteer to find the limits and see how the systems react too. When I was a youth I did this because it's fun, but these days I do it to ensure I know the limits of the car and the road.What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
mollymoo said:
I have, lots, specifically to learn the limits. I've done it in a variety of conditions on a variety of surfaces. Every winter if there's a clear stretch of road and it's safe to do so I'll test the limits of traction so I know what the limits are [/]in that car, in those conditions[/] - this used to mean locking up or spinning the wheels, but now involves squeezing the stop or go pedals till the systems kick in. I've induced understeer and oversteer to find the limits and see how the systems react too. When I was a youth I did this because it's fun, but these days I do it to ensure I know the limits of the car and the road.
What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
Interesting, ta! I'm going to hazard a guess that you have done skid pan training or at least some kind of sandboxed experience. How do you mitigate the risk of losing control when attempting to find the limit on the road? I mean this in any sense but mostly in terms of skills & preparedness.What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
mollymoo said:
I have, lots, specifically to learn the limits. I've done it in a variety of conditions on a variety of surfaces. Every winter if there's a clear stretch of road and it's safe to do so I'll test the limits of traction so I know what the limits are [/]in that car, in those conditions[/] - this used to mean locking up or spinning the wheels, but now involves squeezing the stop or go pedals till the systems kick in. I've induced understeer and oversteer to find the limits and see how the systems react too. When I was a youth I did this because it's fun, but these days I do it to ensure I know the limits of the car and the road.
What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
Me too, especially in the wet. Personally, I find it very informative to invoke wheelspin, as it lets me know how much (or how little) grip I have. However, I run a lot of power through the front wheels, so its a) very easy and b) very safe. I rather doubt if I would be so brave if it was RWD. What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
Quite often I'll test cornering grip by steering too hard to see how close I am to the limit of grip. Again, very easy to induce and recover in a planted FWD car - probably wouldn't do it in a squirrelly RWD
I would point out that I would only ever consider doing this where the result of getting it wrong would be confined to embarrasment, rather than bent mechanicals or where it would force other vehicles to take avoiding action.
In my mind, the best few quid I've ever spent was on a trackday in the torrential rain and also a skidpan session - both were hugeley entertaining and amazingly educational - everyone should try it
I made a spreadsheet to work out my cars stopping distances with different brake setups, apparently mine as stock can stop in 30.2m from 50mph. The minimum if all four tyres were bought to the simultaneously limit of adhesion would be 28.7m.
Obviously there are a few too many assumptions in there for it to be 100% accurate, but it doesn't seem too far off real world results.
Obviously there are a few too many assumptions in there for it to be 100% accurate, but it doesn't seem too far off real world results.
What's your stopping distance at 50mph?
I have the use of 2 cars.
In the one car, I once had to brake for an emergency - it stopped so hard I suffered a severe burn to my chest from the seat belt which took a weeks to completely heal. In the wet and on a road slippery with cow slurry and mud.
Had I been driving the other one I would probably have sailed straight into the oncoming car, over his roof and some distance beyond!
I have the use of 2 cars.
In the one car, I once had to brake for an emergency - it stopped so hard I suffered a severe burn to my chest from the seat belt which took a weeks to completely heal. In the wet and on a road slippery with cow slurry and mud.
Had I been driving the other one I would probably have sailed straight into the oncoming car, over his roof and some distance beyond!
MatthewO said:
Thanks to its underpowered servo, and assuming it will ever make it to 50mph, my mk1 Golf takes just under 32 miles to stop...
A servo? you posh bar-steward! 
My stopping distance from 50 needs to be measured in miles rather than yards/feet, that's my excuse for not hitting 50 much
mollymoo said:
I have, lots, specifically to learn the limits. I've done it in a variety of conditions on a variety of surfaces. Every winter if there's a clear stretch of road and it's safe to do so I'll test the limits of traction so I know what the limits are [/]in that car, in those conditions[/] - this used to mean locking up or spinning the wheels, but now involves squeezing the stop or go pedals till the systems kick in. I've induced understeer and oversteer to find the limits and see how the systems react too. When I was a youth I did this because it's fun, but these days I do it to ensure I know the limits of the car and the road.
What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
I most probably fall into the 'im young, its fun' group but I would intend the reply in agreement with the above.What I've learnt informs my driving every single day. I find it quite scary most people on the road have no idea about where the limits are or what the car does when it reaches them. We should have skip pan training like the Finns, then maybe people would drive to the conditions.
I have done a skid pan experience, it was insightful but I have had more fun with usual driving than they allowed in messing about.
trashbat said:
In 2001, the AA reckoned that my car had a minimum 26m stopping distance at 50mph, under sudden braking with a 22kg pedal load.
And there's the real main difference between old brakes and new ones. My 1969 Triumph 1300 (disks front / drums rear / no servo) will virtually match your 26m (best is 26.3m) but it takes around 118lbs (53Kg) of pedal pressure to do so. Which tends to remind you that you were driving too close when you had to hit them that hard
As for the Highway Code distances, they were calculated assuming roughly 67% braking efficiency (0.67g deceleration). Even an Anglia with drums all round could comfortably better that - our all-drum Dafs will give 90% with the limit being the tyres.
In most cases, certainly on motorways, it's the "thinking time" that causes problems because it's extremely unlikely that the car ahead will literally stop dead. And thinking times are a problem because, if you ask anyone they'll swear blind that they have lightning fast reactions - they react literally "as soon as they see a need to". But, by definition, no-one is aware of the time it takes themselves to become aware of the need to and that's all part of their real reaction time.
That's what accounts for the second or (considerably) more from when the brake lights of the car 1/2 a second ahead come on to when they react with their own brakes - by which time it's either too late, or causes the whole motorway to some to a stop as a cascade of ever-harsher braking happens with the numpties who've also left not enough time behind them.
As for the test of "self driving" cars, follow-the-leader with telemetry being provided by that leader isn't all that difficult or impressive. In fact, it's only what those things called trains have been doing for over a century, just using solid links instead of wireless ones
Variomatic said:
In most cases, certainly on motorways, it's the "thinking time" that causes problems because it's extremely unlikely that the car ahead will literally stop dead. And thinking times are a problem because, if you ask anyone they'll swear blind that they have lightning fast reactions - they react literally "as soon as they see a need to". But, by definition, no-one is aware of the time it takes themselves to become aware of the need to and that's all part of their real reaction time.
Yes - but IMO the thinking time is much longer than the Highway Code figures. It's not the time it takes to see something and switch pedals, it's the time it takes to see something and begin braking with the correct amount of pressure - which might actually not happen until the 'oh s
t' moment halfway through ordinary braking.trashbat said:
es - but IMO the thinking time is much longer than the Highway Code figures. It's not the time it takes to see something and switch pedals, it's the time it takes to see something and begin braking with the correct amount of pressure - which might actually not happen until the 'oh st' moment halfway through ordinary braking.
Exactly. A big part of that time can be taken up just getting the signal from your eyeballs to your brain and having your brain recognise it as a hazard. You only become aware of the need to act once that's happened and it doesn't matter how fast or accurate your "reaction" is after that point (which is the reaction time you're aware of) if it's taken you 2 or 3 seconds to register the hazard in the first place. t' moment halfway through ordinary braking.That's the part of reacting that drink, drugs and tiredness affect - the time it takes your brain to become aware of the threat, which is time you simply can't be aware of. Which is why people don't realise just how impaired their abilities are by those things.
)whic I find quite alarming!Don't forget that "best" distances are just that - on a clean, dry, and good road surface. Rain will obviously affect them (doubling is often quoted), but the greasy ste left behind after rain and potholes / irregular road surfaces that try to break the tyres' grip when you hit them can have almost the same effect.
Given the recent weather (1) and / or (2) above will have been factors on Saturday and I can't think of anywhere in the UK nowadays where you can be sure that (3) isn't as well! All the more reason to leave far more than the "minimum" 2 second gap, even when conditions seem good, rather than (as many do) less!
te left behind after rain and potholes / irregular road surfaces that try to break the tyres' grip when you hit them can have almost the same effect.Given the recent weather (1) and / or (2) above will have been factors on Saturday and I can't think of anywhere in the UK nowadays where you can be sure that (3) isn't as well! All the more reason to leave far more than the "minimum" 2 second gap, even when conditions seem good, rather than (as many do) less!
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