Modern safety systems and badly placed speed limit signs.

[Jon39]

Driving along at 70 mph perfectly legally on the M25, then suddenly your car slows, by itself, to 40mph.
Quite a hazard, when following vehicles without the same safety systems continue at 70 mph.

This photo shows the reason for what happened.





An advanced driver might steer on to the hard shoulder to avoid possible rear end collisions, although Lane Assist might not permit that manoeuvre.

[waremark]

Everyone I've asked switches these ADAS systems off every time they start the car (as I do).

[TheDrownedApe]

There is a similar sign on the m54 just after junction 2 that our old iD3 used to pick up and auto brake to jatch it.

We had all the assist functions turn off too

[BlindedByTheLights]

It has been turned off in our car for three years due to the same issue.

There is even a safety alert from national highways about use of speed signs in roadworks causing this issue:

https://www.highwayssafetyhub.com/uploads/5/1/2/9/...

[TomTheTyke]

It’s unfortunate nobody in government (that I’ve heard) seems to be looking at this seriously and critically.

They must know it’s bad as a good number of them must use cars with these systems, but they don’t seem willing to allow that this has gone too far.

NCAP ratings were fine for airbags and crumple zones but this is dangerous, yet everyone goes along as though it’s a natural continuation from the above.

[DFT5215]

If your car is anything like mine, momentarily overriding the cruise control with throttle application (and it's wholly a pedal position thing, so you don't have to accelerate) turns the system off and you don't slow down.

I've turned it off permanently and mine was smart enough to slow down for corners and roundabouts.

[sixor8]

My eNy1 doesn't slow down, it beeps at you and flashes the speed symbol on the dash. I leave all mine on.

This happens near me, there's a side road with a 20 mph sign that some wag has twisted slightly. I wouldn't want a car that does that!

Lane 'assist' is just that, it's easily overcome.

[saknog]

There is a stretch of road North of Norwich where locals put up protest signs wanting a 40mph speed limit in a 60mph zone. It showed a 40mph speed sign with wording “we need” above it.
These signs are placed in from the verge but still picked up by my car, which I ignore, and have the limiter switch off. People not aware of this kept getting caught out and slowed down unnecessarily.
Some have now been removed but the speed limit has been officially reduced to 50mph anyway.