Relationship between speed and safety

[MGF]

Quite. No need for a long discussion on this one.

[Silk]

Quite. No need for a long discussion on this one.

No. NOT quite. Travelling on a busy motorway where all other traffic is flowing freely at around NSL. Is it safer to travel at 70 or 40.

It's safer if everyone travels at 40. The more you increase speed in relation to the static environment or other vehicles, the more you increase the risk.

Blanket statements like, "slower is always safer" are rarely absolutes and merely serve to demonstrate limited thinking.

I accept that driving slower isn't the answer to all our problems when it comes to road safety. But the vast majority of the motoring public have rejected further training, so speed is all we have left. People simply don't care how well they drive, so we have to reduce their speed in order to mitigate the inevitable. It's a shame for those of us who believe that being a better driver is the answer, but there you go.

[fungus]

Quite. No need for a long discussion on this one.

No. NOT quite. Travelling on a busy motorway where all other traffic is flowing freely at around NSL. Is it safer to travel at 70 or 40.

It's safer if everyone travels at 40. The more you increase speed in relation to the static environment or other vehicles, the more you increase the risk.

Blanket statements like, "slower is always safer" are rarely absolutes and merely serve to demonstrate limited thinking.

I accept that driving slower isn't the answer to all our problems when it comes to road safety. But the vast majority of the motoring public have rejected further training, so speed is all we have left. People simply don't care how well they drive, so we have to reduce their speed in order to mitigate the inevitable. It's a shame for those of us who believe that being a better driver is the answer, but there you go.

Lets all stay at home and not go out on the road. Zero speed = zero accidents

[MGF]

The net result of less speed - all other things being equal - is less harm ( not necessarily fewer accidents).

The fact that we can identify specific situations in which less speed results in more harm isn't relevant to the net benefit of reducing the speed of traffic.

Limits will continue to be reduced until it is no longer politically and/or economically viable to do so. At that point the authorities will need to be more discerning or even just discerning when setting limits.

[Horse]

No. NOT quite. Travelling on a busy motorway where all other traffic is flowing freely at around NSL. Is it safer to travel at 70 or 40?

Errr . . . isn't any danger as a result of dangerous driving by the faster drivers approaching from the rear?

[Horse]

The net result of less speed - all other things being equal - is less harm ( not necessarily fewer accidents).

It's also exposure to fewer hazards in the same timespan, with shorter reaction distances and stopping distances when necessary.

It would be rather perverse to argue against that, effectively saying that more hazards, reduced reaction time and extended braking distances = either 'as safe' or 'safer'!

[akirk]

to return to the point - lower speed doesn't always equal safer...

Actually, it does. If everything else is equal.

And if you can find a single place / time / situation where everything else is equal then I would agree...

but as shown in detail above, rarely is everything else equal, so lower speed = safer is a theoretical concept only - it is not reality...

Alasdair

[Horse]

lower speed = safer is a theoretical concept only - it is not reality...

You can't seriously think that?

Which bit of this is incorrect?

exposure to fewer hazards in the same timespan, with shorter reaction distances and stopping distances

How can that not be safer? *


* Excluding suicidal pedestrians with a bag full of scrambled egg and broken biscuits

[Kimosabe]

As has been frequently mentioned, observation and/or the lack of, is one of the biggest factors affecting outcomes. Simply reducing speed limits (while not enforcing them) is far too simplistic and irregular enforcement clearly doesn't work. The flip side of that is that penalisation only works sporadically, so the solution is better driver education and routine retesting, with the caveat of having to pass in order to maintain a full license or else be demoted. That would put a strain on public transport and lighten traffic congestion for sure.

Wouldn't graduated licenses with graduated exemptions affect this positively? 'Red, Amber, Blue and Green' licenses are a pet theory of mine.

Drivers could hold badged 'Learner' status (red) until they pass their test. If they pass, badged 'Probationer' (amber) for five years after passing (with a restriction to non electric and unmodified cars of upto 1000cc) and a retest at the end of their term. If they fail the retest, they would instantly revert to badged 'Improver' (Blue) should they either be found in breach of the HC/RTA or fail their retest. This would mean that they could only drive with a 'Full' license holder as a passenger and then revert back to 'Probationer' for another two years. If they complete this, then they qualify as a 'Full license holder' (green) pending a five-yearly retest. Apologies for colours but having coloured letter stickers in the windscreen is a good thing, in my book as it serves as a constant reminder to achieve what is expected.

Just a thought.

[Gareth]

Which bit of this is incorrect?

exposure to fewer hazards in the same timespan, with shorter reaction distances and stopping distances

How can that not be safer?

Oh, an easy question I can answer! If, as a result of being forced to travel slower, a driver is bored and/or paying less attention.

[Horse]

No. NOT quite. Travelling on a busy motorway where all other traffic is flowing freely at around NSL. Is it safer to travel at 70 or 40?

Errr . . . isn't any danger as a result of dangerous driving by the faster drivers approaching from the rear?

Are you seriously contending that if a driver has the option flow at 70 along with everyone else but makes a conscious decision to travel 30mph slower, then they are not the danger... it's everyone else?

Drivers approaching from behind have, apparently, carte blanche to drive into another vehicle because they're not looking ahead and reacting? That seems to be your alternate view.



And if you think I'm being flippant, a lot of my day job is dealing with the way in which drivers approaching intentional obstructions on motorways, whether at roadworks or incidents, can't deal with them safely. I'm very well aware of how poorly many drivers react to things which are far more obvious than a car ahead travelling at 40mph.

For example:
https://www.youtube.com/watch?v=ABuVWdmYFno

This video (featured on BBC's The Motorway programme) was recorded from an HA Traffic Officer Vehicle attending an incident. The TOV was displaying beacons, and the Red X signs were on the gantries. The same vehicle was written off by another driver a few weeks later, while at another incident. I had been at another incident, with that vehicle, just a few days before that video was recorded.

https://www.youtube.com/watch?v=yhZSEIn9t2k
I spend time at the roadside in roadworks too. Drivers colliding with tapers (1m high cones, 135m of them, with sequential flashing lights, are often hit, as are the road works vehicles:
https://www.youtube.com/watch?v=q96fzeguyas
Scroll along to 1:40 and watch . . .

The first thing I do when stopping at the roadside is look for somewhere to jump to . . .

[Horse]

Which bit of this is incorrect?

exposure to fewer hazards in the same timespan, with shorter reaction distances and stopping distances

How can that not be safer?

Oh, an easy question I can answer! If, as a result of being forced to travel slower, a driver is bored and/or paying less attention.

Good luck with getting the opposite through the DfT as justification for raising limits

[akirk]

lower speed = safer is a theoretical concept only - it is not reality...

You can't seriously think that?

Which bit of this is incorrect?

exposure to fewer hazards in the same timespan, with shorter reaction distances and stopping distances

How can that not be safer? *


* Excluding suicidal pedestrians with a bag full of scrambled egg and broken biscuits

you are of course completely right, (and wrong!)
the key in all of this discussion is that some points are accurate - but only in isolation - and real life is never that simple... the problem is that people fixate on the simplistic soundbites because they are easy to understand - whereas reality being more complex means that we are setting policy based on assumptions / theory, rather than reality.

lets take the above:

lower speed = safer
& exposure to fewer hazards in the same timespan with shorter reaction distances and stopping distances

sounds logical

Scenario 1
if you have a car on its own driving up a road then the logic is absolutely fine - assuming the only hazards to be non dynamic ones (corners / ditches / etc. - not cows / motorbikes / dive-bombing golden eagles) then those two statements are 100% accurate - but that is so far away from normal reality that it is not helpful - in reality situations that simple rarely lead to accidents, so they shouldn't be used as the basis for determining policy to try and reduce accidents - they are statistically insignificant.

Scenario 2
Lets add in one hazard - we can choose from a wide selection, but lets add in an easy one - 18 year old male driver having just passed his test...
He is approaching from behind...
The slower we drive, the more likely he is to overtake us - increasing risk of an accident
If we are doing 60 - he might decide not to overtake
Lets drop our speed to 40 - he might now overtake, if there isn't really room, then our going slower has made the situation less safe & exposed us to a greater number of hazards - ergo the quoted statements above do not apply in this scenario

(equally speeding up to 70 might encourage him to race - esp. if cars involved might encourage that - could also decrease safety - it is a complex relationship of factors)


and we can think of many more:
- farmer coming out of a field - anticipating swinging out behind us, we slow - oops 1/2 tonne of finest manure into your convertible
- you overtake said farmer - the slower you go the longer you are out - the greater the exposure to the hazard
- motorcyclist comes along a road - three cars ahead each going at c. 55 with space inbetween - easy to get past - you in the front car decide to slow down - safer? - no you now have three cars bunched up and it is a bigger hazard for the motorcyclist

and no doubt many many more

the point is that slower speed = safer is fine as a concept - but it is not that simple in real life - of course there are many many scenarios where going slower would be a good idea and of course safer - hence my comment above ref. AD meaning that you might drive faster than others at times, but also very often slower than others - speed is one of many many complex factors in driving and safety - the one thing that is clear is that there is no simple correlation between speed and safety - hence the reason why those who consider the bigger picture and don't hang onto soundbites will usually talk about appropriate speed being the correct concept...

It is an easy metric to measure and that is the only reason why there is so much emphasis on speed - but we should be promoting an intelligent approach to driving not a dumbed down one based on flawed logic.

And as advanced drivers we should be driving our car for the whole scenario - ie we should be conscious of and take into account not just ourselves and the road, but other road users and those around...

Alasdair

[Horse]

the key in all of this discussion is that some points are accurate - but only in isolation - and real life is never that simple...

lower speed = safer
& exposure to fewer hazards in the same timespan with shorter reaction distances and stopping distances

sounds logical

. . . but that is so far away from normal reality that it is not helpful - in reality situations that simple rarely lead to accidents

There are some very simple realities. As I've said, faster = etc.

However, in your normal reality (and remember that yours may be very different to mine or anyone else's, like the van driver this morning who was about 2m behind me . . . ), it's the difference in speed which has implications for outcomes. However

The slower we drive, the more likely he is to overtake us - increasing risk of an accident
If we are doing 60 - he might decide not to overtake

By driving faster, what does that do to our safety? If it means we travel faster while overtaking, or passing other hazards, then we - even if for a short duration - may well increase other risks to offset another.

And as advanced drivers we should be driving our car for the whole scenario - ie we should be conscious of and take into account not just ourselves and the road, but other road users and those around...

But that's not the thread. This is simply 'Relationship between speed and safety'.

[Horse]

[quote="Horse] Drivers approaching from behind have, apparently, carte blanche to drive into another vehicle because they're not looking ahead and reacting? That seems to be your alternate view.
[/quote]

[/quote]

So that's a 'yes' then?