Brake testing

[Dr Jekyll]

Trundling along lane 2 of the M25 last night in a line of traffic slowly overhauling lane 1. Up ahead in lane 1 was a Mercedes E matching the speed of the traffic in front but leaving a big gap. Next to me and behind the Merc was a lorry, about as big as non artics come and ridiculously close behind the Merc, certainly less than a car length at 50 ish. Suddenly the Merc braked very hard but very briefly then accelerated, I suspect he was trying to flash his brake lights and misjudged it.

The truck driver jammed on brakes and horn, somehow missed the Mercedes by what must have been inches. But then dropped back to a reasonable distance. I wasn’t best pleased because the lorry driver could easily have swerved into me or I could have been caught up in the carnage if they’d collided, but it has to be admitted this risky move did work, the lorry did drop back.

The moral seems to be, trying to flash brake lights can be just as risky as deliberate brake checking.

[Dr Jekyll]

Coilspring said:

Fair point, but most hgv are not being driven for optimal economy (even though thats what the company/fleet manager wants). More that they are driving to deadlines. They often have to arrive within 15 minute timeslots at warehouses. If later than their timeslot they can be kept for hours until unloaded/loaded. Often the only way to achieve these timeslots is to drive to the speedlimiter all the way.

And the relevance to tailgating is what?

[Dr Jekyll]

Coilspring said:

Dr Jekyll said:

And the relevance to tailgating is what?

I thought it was explained, obviously not. Lorries are (way too often), set virtually impossible time targets. Often the only way to achieve those targets is to drive to the speed limiter (which means they will not let go of any speed unless they have to), even if that means sitting way too close to the vehicle in front, hoping (pressuring maybe) that vehicle to get out the way.

Is it right? No! Do I agree or support it? No! But do I understand why it happens? Often, yes!. The real problem is OFTEN (not always, agreed) the office bods who set the target times by average speed calculators taking no account of the road conditions encountered.

I understand that they are in a hurry, what I don't understand is why tailgating rather than driving 2 seconds behind at exactly the same speed helps them meet their targets. Most of the tailgating I see is of cars in lane 1 doing 50 in 50 limits so they can't get out of the way, even assuming their response to being tailgated would not be to slow down.

[Dr Jekyll]

Coilspring said:

Who is supporting tailgating?

But if you can understand some of the issues you can have an idea of a mindset of some drivers, which can help your own driving, positioning.

I have a better idea. The tailgaters should understand simple physics and stop tailgating.