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?
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?
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?
The 2 second rule was pure thinking outside the box genius, simple to understand, simple to implement and effective.
Out of the box indeed! It is a case of what drivers can easily observe and understand. But let's get back to the topic - speed limits and observation. And to take a line from the initial post:
How do different countries tackle speeding on their roads? What could we learn from them?
I have observed that in some countries, particularly USA and Canada, speed limits are respected much better than they are here. I decided to compare the way speed limits are signed in these places.
UK speed limits for visitors:
No indication at all, as applicable to motorways. Everyone (including foreigners) is supposed to just know that the speed limit is 70 mph - unless a lower speed limit is indicated.
A red-bordered disc with a number within. This shows the actual speed limit past this point. It is used wherever the speed limit changes.
A white disc with a black diagonal bar. This means that the speed limit is 60 mph if a single carriageway and 70 mph if a dual cariageway. (Why on earth can they not just use method 2 above?)
Street lighting. This means that the speed limit is 30 mph unless another speed limit is indicated. (But not on a motorway - see also 5d below.)
Repeater signs. These are smaller than the regular ones announcing the start of a new speed limit, and act as speed limit reminders. They are used:
a. on motorways and dual carriageways where a speed limit lower than 70 mph applies,
b. on single carriageway unlit roads where a speed limit lower than 60 mph applies,
c. on lit roads where a speed limit above or below 30 mph applies.
d. They are prohibited on lit roads where the speed limit is 30 mph, except on motorways, where they are allowed if applicable.
North American speed limits for visitors:
A number in a rectangular panel shows the speed limit from this point forwards (regardless of class of road or whether it is lit).
Um ... that's about it.
Likewise, many European countries have a far simpler system than the UK. For example, in Sweden the maximum speed anywhere is 110 km/h. This is indicated by a red-bordered circle with the figure 110 inside it. Simple! Much clearer than a diagonal black bar. The problem in the UK is that they are indicated in such a complicated way, as a result of many amendments to the law since the thirties. Also they do not always relate to road conditions. I have driven many thousands of miles in the USA but have yet to see there the speed limit go up as one proceeds from a major road to a lesser road. Perhaps that is part of the reason why speed limits are better observed in N America. I don't envy foreigners driving on our roads and trying to understand our speed limits.
One advantage of the diagonal black bar is that the maximum speed limit may depend on what class of vehicle you may be driving. The speed limit for a truck can be different for a car on the same stretch of road. The black bar sign simply says "national speed limit applies from here on".
There are many factors such as the state of the road and the braking system of the vehicle, which can affect the stopping distance of a passenger car, but usually, under normal road conditions, if you are traveling at 30 mph, your stopping distance is 45 meters. If you double the Your speed to 60 km / h, the kinetic energy of your vehicle is square, so your vehicle stopping distance is also four times (4X45 = 180). Also, keep in mind that most people, on average, take seconds to respond to a dangerous situation until the brakes are applied, so you will also need to add the distance to respond and apply the brakes. Example: If you are traveling at 60 mph, you are driving at 88 meters per second. Therefore, if it takes you one second to respond to danger and apply your brakes, you will need to add 88 meters to the above number for stopping distance (180 energy requirements Kinetic + 88 meters response time = 268 meters). Distance difference from 100 km / h (real world test) The table below shows the distance of the car from 100 km / h. These cars have been tested at different places on different days. Be careful when comparing results as test results can vary depending on many factors including the surface, how speed is measured (as different cars have different speed gauges), tire pressures, fuel load and whether the car was just a single driver or were there additional passengers
