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?
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.
That equation seems a bit lacking, surely the design, construction, materials, size and inflation pressure of the tyre needs to be taken into consideration, no?
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.
. . . 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.
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?
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 TODdry = Max {TODN -1,1.15TODN}
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 ASDdry =Max{ASDN-1,ASDN }
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
