====== adaptive cruise ======
My car has an adaptive cruise control system. Adaptive cruise is a variation on traditional fixed-speed cruise control that adds the ability to maintain a follow distance from a leading car. For example, the adaptive cruise system can be set to 80mph and will keep the car going 80mph as long as there's no vehicle in front of it. If it comes up behind a lead vehicle that is going slower, say 65mph, then it will slow to 65mph and maintain some reasonably safe following distance, say 25m. This is quite useful because it eliminates the need to adjust cruise control settings to accommodate slower traffic.

I've illustrated this scenario with a diagram. The actual speed of vehicles is denoted with ''(parentheses)'' and the adaptive cruise control setting with ''[brackets]''. ''L'' is the lead car and ''C'' is our car. Let's say each "." character is about 5 meters.

<code>
L (65)
.
.
.
.
.
C (65) [80]
</code>

Everything is fine here. Now let's get on the highway, introducing another lane (''|'') and two more vehicles. One of the vehicles ''X'' is adjacent to our lead car and the other ''F'' a is a driver following us.

<code>
L (65)      | X (65)
.           | .
.           | .
.           | .
.           | .
.           | .
C (65) [80] | .
.           | .
.           | .
F (65)      |
</code>

Our car ''C'' is maintaining a safe follow distance of about 25 meters from the lead car, courtesy of its ACC system. But the speed limit is 80mph and ''F'' wants to go 80mph. Looking at the diagram it's clear that there's no scenario here that is going to allow ''F'' to go 80mph unless ''L'' or ''X'' decides to change their speeds.

Virtually every time I find myself in this scenario (driving ''C''), ''F'' decides to overtake and merge in between ''C'' and ''L'', ending up offset by about 25 meters from their original position but still traveling at their original speed of 65mph.

<code>
L (65)      | X (65)
.           | .
.           | .
F (65)      | .
.           | .
.           | .
C (65) [80] | .
</code>

Now we no longer have the desired 25m follow distance from the car in front of us, so the ACC system briefly slows the vehicle to create the gap then resumes cruising at 65mph.

<code>
L (65)      | X (65)
.           | .
.           | .
.           | .
F (65)      | .
.           | .
.           | .
.           | .
.           | .
.           | .
C (65) [80] | .
.           | .
.           | .
G (65)      | .
</code>

Oh look, we have a new follower ''G''...I wonder what will happen next...

And so it goes. I have had this happen countless times, I even get the finger or see the driver yelling at me as they pass by.

Hence the dilemma: Do you use the system that automatically maintains a safe follow distance resulting in getting verbally abused and which causes others around you to drive in an unsafe manner? Or do you keep an unsafe follow distance to prevent that behavior?

In the specific situation here, the best action is to get into the right hand lane and wait until the situation in the left hand lane improves. However, in practice this frequently occurs when ''L'' is going marginally faster than ''X'' (e.g. 65mph), so you will pass them eventually and it makes sense to stay in the left hand lane, in which case you are subject to the behavior.

The general phenomenon isn't limited to adaptive cruise. In general, the safer you drive the more upset other people will be at you.

I have yet to draw any worthwhile conclusions from this phenomenon.

{{tag>from_blog technology humanity}}