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**log in**There have been many reports of motorists using the lack of traffic on the roads during the Covid19 lockdown to flout the speed limits and now with more traffic back on the roads there is a danger that some may continue to drive at excessive speeds even after things are back to ‘normal’.

Behavioural Science in transportation (understanding the behaviour and motivations of transport users such as motorists and rail commuters etc) is a fascinating subject which plays a big part in the engineering and design of roads and their ‘furniture’ in an attempt to gently persuade drivers to modify their driving behaviour to something more appropriate.

There are many such psychological tactics in place to combat speeding but could we be doing more? What other engineering solutions could be implemented to stop excessive speeding? How do different countries tackle speeding on their roads? What could we learn from them?

Nevertheless, technological fixes are not the full answer - they will mostly help drivers who are generally compliant. What we need is a better understanding of what makes non-compliant drivers tick. We'll be organising, next year through the IET, a seminar on behavioual issues in transport. Our previous seminar has highlighted both the complexity and potential of behavioural understanding in tackling road safety issues.

Your reply to Deborah's question is very interesting and informative with regards to ISA. However, as a Human Factors facilitator I would be very interested in behaviour issues and what makes a non-compliant driver tick. If you require any assistance with this seminar, please do not hesitate to contact me.

Kind regards,

John

**recorded presentations**we filmed at the first Behavioural Science in Transport event a few years ago, which may be of interest to you and other community members.

Thanks for your post on the topic, the ISA looks to be a useful piece of technology. I'm looking forward to planning our seminar for next year and holding the third event in our series on the subject of Behavioural Science in Transport.

If the question seeks to understand ways to address speeding in the medium to long term then Alan's answer is very relevant and it's good to know technological solutions are on the horizon. With my systems engineering hat on, I think it's important to explore the question further to understand the underlying needs of the various stakeholders.

There are a lot of tacit assumptions underlying the question and to develop a well-engineered (not necessarily wholly technical) solution it is important to understand the needs and the variables in play.. Why are we trying to reduce speed? To reduce accidents, reduce fuel consumption, nudge drivers towards other forms of transport that are too slow, ... Who benefits from a reduction in speed? The driver, other road users, the environment, nearby residents ... In what ways do they benefit? Lower risk of injury/death. lower fuel bills, cleaner air, less noise?... How can we reduce speed, what solutions exist or could be developed? What is the time frame for reductions, are there targets to meet or that need setting? How much do we need to reduce speed by? Does everyone's speed need to be the same? How will we know when we've done enough? How do political considerations affect engineered solutions?

Speed limits are a fairly blunt tool, they don't take into account driving ability, which can be affected by skill level, fatigue, distraction, weather, other drivers... In a world of increasing electfication, connectivity and automation, maybe speed limits could go up in certain circumstances. Perhaps autonomous cars will be able to safely drive much faster with zero emissions, so why do they need to go slowly? How is that affected by the human drivers near by? With connected vehicles, or vehicles with advanced sensors, could the car vary its own speed limit to adjust to local conditions?

Just some food for thought, I'm not advocating anything here.

So two factors, in line with the other points raised in this thread, one is whether it would be possible to produce a camera based system that analysed the road ahead for visibility and road conditions and advised maximum safe speed. The other, and I'm being perfectly serious here, is that there is a strong correlation between people who choose to live in rural areas and people who don't like being told what to do. Hence if solutions can be developed to address some of the risks associated with this speeding problem then I'd have thought it would make a good benchmark for other situations.

Nice set of data here (pages 15-39), although does rather focus on the young and the elderly, and doesn't seem to clearly mention false sense of security due to over familiarity: https://www.cornwall.gov.uk/media/31847071/risk-based-evidence-profile-2018.pdf

Cheers,

Andy

I hope you like it,

The response distance is the distance you travel from a hazard detection point until you start to brake or turn.

Response distance is affected by:

Car speed (proportional increase):

2 x higher speed = 2 x longer response distance.

5 x higher speed = 5 x longer response distance.

Your response time.

Usually 0.5 - 2 seconds.

For 45 - 54 year olds the best response time in traffic.

18-24 year olds and people over 60 have the same reaction time in traffic. Young people have sharper senses, but older people have more experience.

Response distance can be reduced by -

Expectation of casualties.

Readiness.

Response distance can be increased by -

Decision-making necessity (e.g., whether braking or steering out of the way).

Alcohol, drugs and drugs.

tiredness .

Easy Method: Calculate the response distance

Formula: Remove the last digit quickly, multiply the response time, and then 3.

An example of a 50 mph speed calculation and a second response time:

50 mph ⇒ 5

5 * 1 * 3 = 15 meter response distance

More accurate method: Calculate response distance

Formula: d = (s * r) / 3.6

d = response distance in meters (to be calculated).

s = speed per hour.

r = response time in seconds.

3.6 = Fixed figure for converting km / h to mph.

An example of a 50 mph speed calculation and a second response time:

13.9 meters response distance = 3.6 / (50 * 1)

Braking Distance:

Braking distance is the distance the car travels from the point where you start braking until the car stands still.

Braking distance is affected by:

Vehicle Speed (Square Increase; "Raised to 2"):

2 x higher speed = 4 x longer braking distance.

3 x higher speed = 9 x longer braking distance.

The road (gradient and conditions).

Rush.

Brakes (mode, braking technology and some brake wheels).

Calculate the braking distance:

Reliable braking distance calculations are very difficult to achieve as road conditions and tire grip can vary greatly. For example, the braking distance may be 10 times longer when there is ice on the road.

Easy Method: Calculate the braking distance

Conditions: Good and dry road conditions, good tires and good brakes.

Formula: Zero the velocity, multiply the figure by itself and then multiply by 0.4.

The figure 0.4 is taken from the fact that the braking distance of 10 km / h in dry road conditions is about 0.4 meters. This is calculated by researchers who measure the braking distance. Square with the speed increase.

Example of 10 km / h speed calculation:

10 mph ⇒ 1

1 * 1 = 1

1 * 0.4 = 0.4 meters distance braking

Example of 50 km / h speed calculation:

50 mph ⇒ 5

5 * 5 = 25

25 * 0.4 = braking distance of 10 meters

More accurate method: Calculate braking distance

Conditions: Good tires and good brakes.

d = braking distance in meters (to be calculated).

s = speed per hour.

250 = a permanent figure that is always used.

f = coefficient of friction, about 0.8 on dry asphalt and 0.1 on ice.

Example of calculating 50 mph on dry asphalt:

Stopping distance

Stop distance = response distance + braking distance

Calculate the stopping distance using these easy methods

It's summer and the road is dry. You drive at 90 mph with a car with good tires and brakes. Suddenly you notice a road hazard and braking forcefully. How long is the stopping distance if your response time is one second?

The stopping distance is the reaction distance + the stopping distance. First, we calculate the response distance:

90 mph ⇒ 9

27 feet Response distance = 9 * 1 * 3

Then we calculate the braking distance:

90 mph ⇒ 9

9 * 9 = 81

32 meters braking distance = 81 * 0.4

The two distances are now combined:

Stop distance of meters = 27 + 32

Clarification is important about calculations

The different methods provide different answers. Which should I use?

Use whatever you want. The differences are so small that they will not affect your theory test, since the margins between the alternatives are quite large.

So if the alternatives are 10, 20, 40, 60, it doesn't matter if you get 10 meters in one method and 12.5 meters.

With another - both are of course closest to 10, which is the correct answer

It is actually possible to drive over the speed limit safely (although still illegal).

Appropriate speed, for the conditions and the vehicle, is the key.

I wouldn't want my freedom to drive my car how I want curtailed by over zealous regulation, although the death count on our roads is high when you factor in how many millions of miles are driven by millions of people in millions of cars everyday we are actually quite good at driving.

Chaps,

Thank you for your comments thus far with regards to; ‘what could be done to combat speeding on our roads?’ by Alan Stevens. This can be and is an emotive subject, yet very interesting. I am keeping notes of your comments to us as a question bank and hopefully they will prove very useful.

**Benyamin**, do you have a formula for aquaplaning. Being from the aviation sector we often use Horne’s Formula V = 9 x √P, which exists for calculating the minimum groundspeed for initiation of this of aquaplaning on a sufficiently wet runway based upon tyre pressure where V = groundspeed in knots and P = tyre inflation pressure in psi. The depth of water is > 3mm.

Kind regards,

John

Yes I agree, there are many factors that need to be taken into consideration, but I was trying to keep it simple.

Kind regards,

John

**Benyamin**, do you have a formula for aquaplaning. Being from the aviation sector we often use Horne’s Formula V = 9 x √P, which exists for calculating the minimum groundspeed for initiation of this of aquaplaning on a sufficiently wet runway based upon tyre pressure where V = groundspeed in knots and P = tyre inflation pressure in psi. The depth of water is > 3mm.

Please note this is a simple formula.

Kind regards,

John

Benyamin Davodian:

. . . An example of a 50 mph speed calculation and a second response time:

50 mph ⇒ 5

5 * 1 * 3 = 15 meter response distance

More accurate method: Calculate response distance

Formula: d = (s * r) / 3.6

d = response distance in meters (to be calculated).

s = speed per hour.

r = response time in seconds.

3.6 = Fixed figure for converting km / h to mph.

. . .

I have no wish to question the integrity of Benyamin's long and detailed analysis. However it can be expressed very simply.

Thinking distance in feet equals speed in miles per hour.

For braking distance in feet, divide speed in miles per hour by 20, square it, then multiply by 20.

Example: 50 mph.

Thinking distance is 50 feet. (Very close to Benyamin's calculation of 15 m)

50 divided by 20 is 2·5. 2·5 squared is 6·25. 6·25 multiplied by 20 is 125, which is braking distance in feet.

So overall stopping distance is 175 feet.

A table showing braking distances based on this simple calculation used to be published in the *Highway Code* for many years. Unfortunately in recent issues this has been messed up my the Government's half-baked approach to metrication. Mixing imperial and metric units always complicates things.

If we were to do a thorough job, I am sure that we come up with an equally simple calculation of stopping distances in metres based on speed in km/h.

Also hasn't all the differences and advances in road stone, tyre rubber and braking systems rendered all this pretty useless? In fact do they still expect learners to know this anymore?

I hope this helps you understand.

If I made a mistake I would love to get feedback from you

where G is aircraft weight, S is aircraft wing area and ρ is atmosphere air density. Aircraft takeoff distance and accelerate-stop distance are related to runway condition. A dry runway and a wet runway are different when calculating distances. This article only deals with dry runway. TODdry is short for takeoff distance on a dry runway

*TOD*

_{dry = }*Max {TOD*

_{N -}_{1},1.15

*TOD*

*}*

_{N}In Eq. (3), TODN-1 is the horizontal distance along the takeoff path, with one engine inoperative, from the start of the takeoff to the point at which the airplane is 10.7 meters above the takeoff surface; TODN is the horizontal distance along the takeoff path, with all engines operating, from the start of the takeoff to the point at which the airplane is 10.7 meters above the takeoff surface. ASDdry is short for accelerate-stop distance on a dry runway

*ASD*

_{dry =}*Max{ASD*

_{N}_{-}

_{1},

*ASD*

*}*

_{N }In Eq. (4), ASDN-1 is the sum of the distances below. (i) Accelerate the airplane from a standing start with all engines operating to VEF ; (ii) Allow the airplane to accelerate from VEF to the highest speed reached during the rejected takeoff, assuming the critical engine fails at VEF and the pilot takes the first action to reject the takeoff at the V1 for takeoff from a dry runway; (iii) Come to a full stop on a dry runway from V1; (iv) A distance equivalent to 2 seconds at the V1 for takeoff from a dry runway. ASDN is the sum of the distances below. (i) Accelerate the airplane from a standing start with all engines operating to V1 ; (ii) With all engines still operating, come to a full stop from V1; (iii) A distance equivalent to 2 seconds at the V1 for takeoff from a dry runway

why do you think so?

I would love for you to thoroughly check and update. Thanks

Rob Eagle:

I remember having to learn all this braking distance stuff from the Highway Code, but how many can really visualise how far 175 feet is? I certainly can't.

Also hasn't all the differences and advances in road stone, tyre rubber and braking systems rendered all this pretty useless? In fact do they still expect learners to know this anymore?

I am inclined to agree, Rob, stopping distances are largely academic. It is not easy to visualise distances without definite visual guides. More useful is the "two-second rule". It is easy to estimate two seconds - about the time it takes to say, "Only a fool breaks the two-second rule."

Have braking distances improved over time? I am not so sure. However good the driver or the brakes, ultimately it depends on the coefficient of friction between rubber and asphalt. Since this is a fairly innate physical feature, my guess is that it has not improved by much. I should be very interested if anyone has any reliable data on this. It is probably sensible to stick to the long-established figures for braking to stay on the safe side.

Learners are expected to familiarise themselves with all of the *Highway Code*. I don't know whether they are tested on stopping distances on the theory test - does anyone on this forum know?

someone

I don't know (ask and know it's not a

shame).

I am sorry for the confusion. I am well familiar with aircraft aquaplaning formuli. I should have asked do you have a formula for the initiation for a car aquaplaning?

John

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