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Definitive answer for stopping distances?

Hi all, I've got my theory test this Thursday and I keep faltering on stopping distances when I'm doing my practice tests.

There doesn't seem to be a general consensus on what the answers are - I've just looked in three places online and got three different sets of answers. Also there seems to be a difference between stopping and braking distances? And will I be asked in metres or feet?

I REALLY need to know what the actual answers are.. help?
(edited 11 years ago)
Reply 1
Avatar for ROG.
ROG.
6
NOT CERTAIN HOW THEY DO IT THESE DAYS BUT IN MY DAY I REMEBERED THIS

20mph x 2 = 40 feet
30 x 2.5 = 75
40 x 3 = 120
50 x 3.5 = 175
60 x 4 = 240
70 x 4.5 = 315

But my mental maths has always been good
Original post by ROG.
NOT CERTAIN HOW THEY DO IT THESE DAYS BUT IN MY DAY I REMEBERED THIS

20mph x 2 = 40 feet
30 x 2.5 = 75
40 x 3 = 120
50 x 3.5 = 175
60 x 4 = 240
70 x 4.5 = 315

But my mental maths has always been good


For those mathematically inclined, stopping distance can be calculated using the following:

SD = s + ((s x s)/20) where s is the speed (I would have written it as s + s squared divided by 20) but I can't work out how!

So, stopping distance in feet at 60 miles per hour is 60 + ((60 x 60)/20) = 60 + (3600/20) = 60 + 180 = 240

Hope that helps (and hope I got the formula right :wink:)
Reply 3
Avatar for Fjarskafinn
Fjarskafinn
OP
14
Thanks for the replies, guys.

I'm finding it easier to memorise the stopping distances in metres, and subtracting the thinking distance in order to find the braking distance.

So for 20mph, 30mph.... etc .... to 70mph, I only need to remember 12, 23, 36, 53, 73 and 96 for the overall stopping distance.

Now, for thinking distance, I take the tens value of the speed (2 in 20mph, for example) and multiply it by 3. So thinking distance at 20mph is 6 metres.

So to find the braking distance, I just take 6 from 12 = 6m for 20mph.

It sounds convoluted, but it works for me. Phew.
Reply 4
Avatar for Advisor
Advisor
8
Overall stopping distance = Thinking distance + Braking distance.

Be sure you understand the difference between braking distance and overall stopping distance. Some questions may ask for one, some may ask for the other, so it pays to read carefully.

Multiple choice answers usually give both metres and feet alternatives, so you can learn either metric or imperial, then take your pick.

Original post by Emma-Ashley
hope I got the formula right :wink:
Yes, you did :wink:
(edited 11 years ago)
Is the theory test with stopping distances in meters or feet or both?

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