On 18/03/2013 10:19, Jethro_uk wrote:
On Fri, 15 Mar 2013 13:55:05 +0000, polygonum wrote:

On 15/03/2013 13:46, Jethro_uk wrote:

On the M40, after High Wycombe westbound (J6 IIRC) where the road comes
out of the high-cliffed bit and starts to go downhill, the road lights
finish. Invariably there's a drop in speed of all the traffic by about
20 mph.

Nothing to do with the Stokenchurch-to-Lewknor fogbank? :-)

Doesn't help

Do they speed up when coming from unlit into lit areas?


Actually, yes. Although the incline of the journey in the opposite
direction might have some bearing. But many times I have driven up the
hill, and noticed traffic speeds increase by about 20mph ...

I rather agree but I often find people's choice of driving speed
perplexing. If you go into London on the M40/A40 it is surprising how
many vehicles slow down well below 70 ages before the speed limit
actually drops. And then, once in the 50 mph bit, actually speed up to
60 or so. Similarly in reverse - doing 40 in the 30 but, but staying
down at 50/60 when limit goes back to 70.

One thing I have noticed since having a car with cruise control is that
the choice of speed of the car in front is invariably 1mph less than
mine ...

Oh yes!

Used to have a Saab turbo 16V - that would do almost all motorway work
in fifth, up hill and down dale, without any noticeable slowing down. CC
really highlighted how other vehicles changed speed a lot. I guess some
of that was drivers not using/having CC, and some simply car engines not
able to make it up hills so apparently effortlessly.

--
Rod