Emergency Stop

[Horse]

That's why I posted an exerpt from the abstract . . .

My point is that while the exact detail of why it happens may not be fully understood, it is well understood that drivers tend to steer towards where they are looking. While investigating it further may be of passing interest we (all) already know the tendency against which we must guard.

For me it's more than a passing interest, as I'm involved with road safety research, often dealing with conspicuity issues.

There are a number of issues involved, one of which - phototaxis (IIRC) - involves the theory that people will steer not just where they're looking but also be 'drawn' to bright lights, so it's also known as 'the moth effect'. Put that into the context of brightly-lit emergency vehicles . . . However, it's also strongly debated and - again, IIRC - 'unproven', though it may affect particularly people who are tired or under the influence of 'bottled medication'

There's several more aspect to it, in no particular order:

Expectation; what is the driver expecting to see?

Understanding; once they've seen and recognised something, do they know what to do - or what they're expected to do?

Red advancing blue receding; doesn't affect everyone, but at night some people see blue light as 'closer' than a red light at the same distance

Looming; http://www.theiacp.org/LinkClick.aspx?f ... &tabid=392 Page 12


But it's no secret that highly conspicuous vehicles get hit:
http://blutube.policeone.com/Media/6189 ... way-crash/

[GJD]

But it's no secret that highly conspicuous vehicles get hit:
http://blutube.policeone.com/Media/6189 ... way-crash/

Goodness! The chat in the comments is that he was injured but lived, which is good - looked potentially worse than that to my untrained eye. As an aside, If I'm ever involved in an accident that bad, I hope my ambulance turns up that quickly.

[Mr Cholmondeley-Warner]

Someone posted a pic the other day of one of those lane closure vehicles with the huge flashing amber lights - the driver had suffered several rear-end collisions. Where are people looking FFS?

Edit: it was Malcolm, and it's here

[Horse]

Someone posted a pic the other day of one of those lane closure vehicles with the huge flashing amber lights - the driver had suffered several rear-end collisions. Where are people looking FFS?

Edit: it was Malcolm, and it's here

Did you know that there was a road worker killed on the M4 near Swindon just last week?

[Mr Cholmondeley-Warner]

Wasn't me guv!

[Mr Cholmondeley-Warner]

On the subject of Police vehicles on the hard shoulder, I notice a change in policy in many areas, which is to park the vehicle at an angle with the front end pointing out into the carriageway. While this gives a good view of the side of the vehicle, in the case of a rear end collision it's going to be punted out into the traffic. Wouldn't it be safer to point its nose inwards - even if this doesn't show off the pretty stripes down the side?

Any officers care to comment?

[Horse]

On the subject of Police vehicles on the hard shoulder, I notice a change in policy in many areas, which is to park the vehicle at an angle with the front end pointing out into the carriageway. While this gives a good view of the side of the vehicle, in the case of a rear end collision it's going to be punted out into the traffic. Wouldn't it be safer to point its nose inwards - even if this doesn't show off the pretty stripes down the side?

Any officers care to comment?

I'm not an orificer, but . . .

It's called 'Fend' parking. Nose out (ie right) is fend 'off'.

Have a read of the abstract linked earlier. The idea is to make the vehicle 'pop out' of the background by being 'different' - a vehicle ahead, in-line, may be moving, while a vehicle that has its side in view is unlikely to be part of normal traffic flow.

Have a look at the 'looming' link I posted for additional benefits.

Also, it may be that the approaching driver sees an angled vehicle and picks up that they should also steer in that direction - imagine a parked emergency vehicle obstructing lane 3 - that could imply 'steer left' by parking fend 'in'.

There are disadvantages to consider, such as that rear lighting is not pointing directly at approaching drivers. No problem with the old 'gumball' rotating beacons, but not so good if the lighting is directional.


As to which way if will go when hit . . .

Turn your ABS off, lock up your wheels in a straight line, then apply steering

TBH AFAIK this is untried IRL, such crash tests haven't been done, but computer modelling has.

[Horse]

More:
http://www.highways.gov.uk/aboutus/docu ... sponse.pdf

[redrobo]

When emergency braking, whatever is following is the biggest threat, do you want to stall having stopped before reaching the forward danger and then be hit by a following truck?
ABS gives you the bonus of steering why spoils it by delaying depressing the clutch?

[TripleS]

When emergency braking, whatever is following is the biggest threat, do you want to stall having stopped before reaching the forward danger and then be hit by a following truck?
ABS gives you the bonus of steering why spoils it by delaying depressing the clutch?

I may be mistaken, but in relation to the power of the brakes, I doubt if the effect of the clutch being engaged or disengaged makes much difference, either to stopping distances or the ability to steer.

Your point about avoiding stalling the engine is a fair one. In an emergency stop situation the priority is obviously to stop as quickly as possible; but keeping the engine running to enable you to move again could also be of benefit, assuming the hazard in front of you leaves you room for manoeuvre.

Best wishes all,
Dave.

[Horse]

When emergency braking, whatever is following is the biggest threat, do you want to stall having stopped before reaching the forward danger and then be hit by a following truck?

I'd have thought 'not having quite enough stopping distance' was the primary 'threat' - and one that requires immediate action (whether harder braking or evasive steering).

ABS gives you the bonus of steering why spoils it by delaying depressing the clutch?

Serious Q: How does freewheeling affect ['spoil'] ability to steer?

[TripleS]

Serious Q: How does freewheeling affect ['spoil'] ability to steer?

I don't suppose it does, apart from the small risk of the engine stalling; and if that were to happen you would lose the assistance of the power steering.

Another serious Q: If you were engaged in a rapid series of zig-zags, slalom fashion, would the power steering performance be much reduced with an idling engine, compared with an engine running at higher speed?

Best wishes all,
Dave.

[redrobo]

Sorry I didn't put that very well did I.
ABS has lots of advantages, ie steering, shorter stopping generally. Why spoil the advantage by being hit by following traffic because you have stalled.

[Horse]

Sorry I didn't put that very well did I.

Why spoil the advantage by being hit by following traffic because you have stalled.

I may be being a bit thick here, but why should de-clutching cause the engine to stall?

[Horse]

I was told not to delay depressing the clutch pedal when braking, it being thought that engine braking on modern vehicles was not necessary given the efficiency of the brakes, but the main reason was that, when ABS was active, it is possible for one of the driven wheels to actually rotate backwards. Knowing that those of us on the course would find that hard to believe, we were shown a slow-motion video of an LGV braking hard with ABS fitted and the clutch not disengaged and, sure enough, one of the driven wheels began to rotate backwards.

. When the ABS slightly released braking on one of the wheels which had begun to lock up, the differential allowed the half-shaft to rotate backwards to dissipate the energy from the, still engaged, engine.

Hmmmm . . .

I've seen old cowboy films where the wheels on the stagecoach seem to be rotating backwards