Drafting

[Veloplus]

Whilst travelling on the motorway, I regularly draft trucks, but always applying the two second rule. I find that a considerable number of trucks travel at 51-52mph, which is sometimes slower than I would wish. My ideal is around 55-60 mph which means frequent overtaking of slower moving trucks.

There is a noticeable fuel improvement when drafting, however, it is not for everyone.

[frv]

Agreed - you have to have safety in mind at all times.

[t0msmith]

I've tried drafting them on the bike and constantly found that I get better MPG staying on my own doing 40 - 45mph rather than sitting right behind a lorry doing around 60 mph. This may be down to aerodynamics - bikes are worse aerodynamically than a car due to turbulent air coming off the rider.

[DrivingGenius]

I wouldnt take a "average" stopping distances to seriously tbh. Many of todays cars stop way faster than that. I say do what you feel comfortable with. I normally keep about 2 secs behind anything.

While it is true that most modern cars with efficient brakes and tyres will "stop" in a shorter distance than quoted in the Highway code, the Reaction time (Thinking distance) has not reduced.

The average adult who is fully alert, and more importantly, expecting something to happen, will react in about 0.7 seconds. This will be increased because of distraction, fatigue, poor health etc.

How far will you travel in 0.7 secs?
At 30 mph - 30 feet
At 50 mph - 50 feet
at 70 mph - 70 feet

If you are drafting the only notice that you will have of "sudden" problems ahead will be the brake lights of the truck ahead.
Assuming the the driver has reacted in the average time (at lets say 55 mph) he will already be braking by the time you have reacted. This will inevitably lead to you rear ending the truck.

Please remenber that the 2 second rule is aminimum distance and should be doubled in wet conditions and mutltiplies by 10 in below freezing.