Ok, so I knew those figures were BS, but...

[Grahamm]

Yesterday, having a bit of a ride out, I stopped off at the Park and Ride carpark near Winchester to practice some slow speed riding and, when I'd finished, I decided to try something I'd always meant to give a go...

There's a long straight section with a line across it, so I ran the bike up to 30mph and as I crossed the line, did an emergency stop, then got off and measured it. I also did the same at 40mph.

Unsurprisingly, although the Highway Code says that on a dry road in good conditions it takes 23m to stop at 30mph and 36m at 40mph, I found that my stopping distances were (including allowing distance for my reaction time of 0.24 seconds) actually 18m and 25m respectively.

Now, ok, I know that those the HC figures were based on a 1960's car with 1960's brakes and tyres on a 1960's road surface and I know that they're unlikely to change them because they'd prefer people to err on the side of caution (and not everyone has good reactions) but at least I know now what my stopping distances actually look like at those speeds and it gives me a better idea of how much space I allow to enable me to "stop in the distance I can see clear on my side of the road".

Useful info

[dolau]

interesting

[Fazerider]

Interesting, though won't it have effectively excluded reaction time from the test? I mean you knew you were going to hit the brakes as you crossed the line, so could judge it much tighter than .24 seconds.

[BIG MAC]

 

[Grahamm]

Interesting, though won't it have effectively excluded reaction time from the test? I mean you knew you were going to hit the brakes as you crossed the line, so could judge it much tighter than .24 seconds.

As I said "including allowing distance for my reaction time of 0.24 seconds".

What I did was take the distance I stopped in from braking as I crossed the line, then added 0.24 * 13.4 m/s (for 30mph) to that, and a similar addition for 40mph.

0.24s is my minimum reaction time, based on a test that they have at the Ride it Right Events held at Haslemere Fire Station twice a year.

Basically there's a bike on a stand, a couple of lights come on as if a vehicle in front is braking and you have to hit the front brake as quickly as you can, your time is the average of three goes.  (Actually I've slowed down a lot, in my late teens/ early twenties I could do reaction tests in 0.18 of a second!) The Highway Code is based on a reaction time of 0.65 seconds which is very slow (although it probably works for people who drive on auto-pilot)

[Fazerider]

Ah, my mistake.
I did wonder if that was what you meant, but decided it couldn't be because the braking distance you achieved from 30mph comes out slightly greater than the highway code's quoted 14m (unless my maths is letting me down).


The highway code allows about two thirds of a second thinking time with good reason. Reaction time isn't quite the same thing, it might be easy to measure when you know what is going to happen and what you need to do, but often it takes a lot longer to analyse a situation on the road. I suppose that with experience our judgement improves and to some extent that compensates for slowing reaction times.

[locksmith]

Interesting that you can see your stopping distance in front of you as you ride through a built up area.

Maybe it's something we should all do.

I allways remember a traffic cop telling me that at 20 mph, If a child stepped out from the front of a stopped bus and I was level with the back, I would hit them.

[bigralphie]

interesting , in my experience you can’t really replicate the sheer speed of a adrenaline fuelled stop so I bet that fiq could be cut even further

[Bracechenko]

Good work 

[Chillum]

Interesting that you can see your stopping distance in front of you as you ride through a built up area.

Maybe it's something we should all do.

I allways remember a traffic cop telling me that at 20 mph, If a child stepped out from the front of a stopped bus and I was level with the back, I would hit them.

Not if you yank the front brake so hard you hit the deck. In that instance you stop about 1m short. Luckily for all involved, especially as the road was very wet as well.

[Grahamm]

Interesting that you can see your stopping distance in front of you as you ride through a built up area.

Maybe it's something we should all do.

It's something that's recommended in "Roadcraft", but I'd never actually done it before and I doubt many road users who haven't done specialist training have done either.

TBH, given that you have to practice and demonstrate that you can do a safe emergency stop for bike and car tests, it wouldn't be at all difficult to include in a lesson, ie rather than just "ok drive/ ride along until I indicate that you should do an emergency stop", make it "if you did an emergency stop at 30mph right next to that lamp post, where do you think you would finish up? Ok, let's see..."

All I know is that I now know something useful that I didn't know before