Highway Code stopping distance needs urgent review, experts say

stopping distance

New research has revealed that the stopping distance prescribed by the government’s Highway Code is too short. They now believe it could take drivers half as much time again to come to a halt in an emergency. Road safety campaigners have called on the government to undertake an urgent review. They want the stopping distance section of the Highway Code revised.

How is stopping distance calculated?

Experts split the length of time it takes a car to come to a halt into two. These are thinking time and braking distance. Thinking time is what it takes us to identify a hazard then for that message to travel from our brain to our foot and our foot to move onto the brake pedal. The braking distance is the amount of time it takes for the car to come to a halt once we’ve slammed on the brakes. Currently the Highway Code says it should take 12 metres to come to a halt from 20mph, 23m from 30mph and 96m from 70mph.

What should stopping distances really be?

Boffins from transport consultancy TRL examined a wealth of academic data that looks into drivers’ thinking time. They concluded that it takes much longer than the Highway Code estimates for drivers to see, recognise and react to an emergency. While the official thinking time is 0.67 seconds, TRL concluded that the human brain actually takes around 1.5 seconds. This is the figure used by the US equivalent to the Highway Code. And in Canada it’s 2.5 seconds.

Jason Wakeford from road safety charity Brake, which commissioned, the research explained: “We’re calling on the government to increase the stopping distances in the Highway Code as a matter of urgency. Even though car braking technology has improved in recent years, the majority of the overall stopping distance at most speeds is actually made up of the time taken to perceive the hazard and react. Our research shows that average thinking time is more than double that set out in the Highway Code.”

What does this mean?

According to the TRL’s calculations, rather than 12m, it will take 19m for a car to come to a halt from 20mph. That’s more than one and a half lengths of the average car more than the Highway Code. At 30mph, thinking time goes from 9m to 20m. That increases total stopping distance to 34m – nearly three car lengths more than the official figure. And at 70mph, thinking time goes up to 121m. This puts total stopping distance at just more than six car lengths longer than the Highway Code.

Speed 20mph 30mph 40mph 50mph 60mph 70mph
Revised stopping distances 19m 34m 51m 71m 95m 121m

Why Highway Code stopping distances are important

stopping distance

Get your stopping distance wrong and this is what happens

The Highway Code stopping distances are used by learner drivers as a gauge to judge their braking by. If that gauge is faulty and they think they can come to a stop quicker than they really can, they have a greater risk of crashing. Brake’s Jason Wakeford said: “A true understanding of how long it takes to stop a car in an emergency is one of the most important lessons for new drivers. Understanding true average thinking time reminds all drivers how far their car will travel before they begin to brake − as well as highlighting how any distraction in the car which extends this time, like using a mobile phone, could prove fatal.”


11 comments on “Highway Code stopping distance needs urgent review, experts say

  1. Eric Hayman October 6, 2017 8:53 am

    There have been driving simulators around for decades. These can easily be used to see how long it takes for a person to react to, say, someone suddenly walking into the road, or another vehicle driving into the path of the simulator user’s route. Why has this not been done to establish reaction times? And why the vast differences between different countries? Are Canadians really slower thinkers?

  2. chris owen October 6, 2017 9:11 am

    I have always treated braking distance as a matter of personal judgement. The figures don’t make any allowance for road conditions, eg rain. I explained this to my driving test examiner and he agreed with me.

    • Eric Hayman December 7, 2017 10:09 pm

      “I have always treated braking distance as a matter of personal judgement. The figures don’t make any allowance for road conditions, eg rain.” The same could be said about speed limits. Just as no speed limit can be said to be right for a section of road under all conditions (weather, traffic, etc), so it can be said that the Highway Code distances cannot be always right. But hey do give a framework for learners to use. Just as it only after taking a course of lessons and passing the driving test that a learner really starts to learn how to drive; experience is the biggest teacher. And it is experience that really teaches correct braking distances.

  3. Robert McLoughlin October 7, 2017 9:53 am

    So much for current advances in tyre technology; one cannot account for stupid motorists who tailgate, drive too fast in adverse weather, traffic and roads.

  4. raymond stevens October 16, 2017 3:54 pm

    try taking into account the idiot overtaking you at say 50/60/70/80 mph plus suddenly cuts your front wing off, well almost then drops his speed slightly lower than your speed which was probably the limit, staying probably 20 foot in front of you.. Class act that one seen it to often

  5. daveoftruro December 6, 2017 9:28 am

    I’ve had my reaction time tested on simulators and it’s far less than highway code times. The problem is that on the simulator you’re poised, waiting for the event to make you brake. Try driving for five hours,seeing the brake lights on the car in front and then realising it’s an emergency stop. I don’t think you’d approach 1.5 secs.

  6. paul watson December 6, 2017 4:47 pm

    stopping distances were for drum brakes,some new cars still have these on the rear,so
    there has not been a lot of interest in standards of design by the car industry,like every
    thing else it’s all about the bottom line and not a lot about safety.

  7. Robert Henry December 7, 2017 12:07 pm

    Good comment from Robert re tailgating and idiotic speeders!

  8. Steve Michelle December 7, 2017 12:14 pm

    This info update may possibly help learners to understand stopping distances, in order to get the written part of the test passed. But, it has no conection to reality. Under real conditions, stopping distance vary considerably, depending on driver, road condition, type of car, and possible distraction. Best solution, look where you are going at all times, don’t drink and drive, don’t take drugs, switch off mobile phones, and never reset sat nav on the move.

  9. Martin Leaver December 7, 2017 12:21 pm

    The Highway Code does say that distances should be doubled on wet roads.

  10. Stanley McWhirter December 7, 2017 5:51 pm

    Drivers think that as speed increases stopping distance increases; actually stopping distance increasingly increases, i.e. an exponential amount. As a driving instructor a favourite question to my pupils was – at 20 mph it takes 40 feet so at 40 mph how far to stop? The usual answer was 80 feet whereas it is actually 120 feet.
    Spotting a hazard early and easing off the gas early may not slow the car all that much but it reduces the stopping distance disproportionately.

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