Adaptive Cruise Control - a cautionary tale.

[AlanD]

The ACC got caught out yesterday

Travelling city bound along the Monash Freeway at 100 kph (the posted limit) and moving through a gentle right hand bend that required no steering input owing to the road camber.

Quite suddenly the car started an almost panic stop that washed off the speed quickly until I took back control of the throttle.

I'm suspecting that this occurred because there was an almost stationary vehicle on the left hand verge. I'd guess it was moving at between 10 and 20 kph waiting for a traffic gap to pull into.

Because of the bend the ACC beam washed across the slow moving vehicle and believed, since there was no steering input, that the car was running up behind another car in the same lane moving very slowly and commenced a rapid slowing manoeuvre. Thankfully the car behind was not tailgating so there was no collision but a quick glance in the RVM showed a rapid closure rate.

I've had similar situations on a straight road with no concern, so the ACC beam is quite directional and is able to differentiate stationary objects from moving ones. It can also detect cars that pull into the gap I leave to the car ahead and takes no action if they are moving faster than me. If they are moving slower then an adjustment occurs to maintain my preferred separation distance.

Some very clever calculations are being done by the system - but it isn't foolproof as my experience shows.

Cheers