[ReidZB]

I don't get it. The article clearly outlines the factors accounted in the safety score, and vehicle speed is not one of them (at least not directly). Yet the author and apparently others are intentionally driving slowly to boost their score? That doesn't make sense.

You can definitely "game" the score (to an extent) by making unnecessary trips, i.e. driving to give it more data, but driving abnormally slowly on those trips doesn't help anything. That is, unless you think driving 55 mph will help in the measures, but I'm skeptical of that.

The forward collision measure is based on number of miles, so if you drive 100 miles with no warnings, that's scored the same way if you were driving at 55 mph or 80 mph.

For the others (hard braking, aggressive turning, and unsafe following), each computes the percentage of time you spend doing the unsafe thing relative to doing it safely. If you want to improve those measures, you need to actually spend more time braking, or turning, or following at >50 mph and less than 3 seconds distance. Just driving a slow constant 55 mph on the highway won't change those measures at all, as I understand it.

The forced disengagement measure is just whether or not the car put you into autopilot jail for not paying attention while autopilot was active. I'd hope no one is getting put in that jail, but especially not if they're trying to be on their best behavior.

Anyway, from the Tesla FAQ, I find the 'predicted collisions in 1 million miles' formula fascinating:

    Predicted Collision Frequency (PCF) = 0.682854
      x 1.014495^{Forward Collision Warning per 1,000 Miles}
      x 1.127294^{Hard Braking}
      x 1.019630^{Aggressive Turning}
      x 1.001444^{Unsafe Following Time}
      x 1.317958^{Forced Autopilot Disengagement}

Hard braking and forced autopilot disengagement are, in their model, big predictors of a collision. I'm surprised to see unsafe following at such a low weight.

[djanogo]

"vehicle speed is not one of them (at least not directly). Yet the author and apparently others are intentionally driving slowly to boost their score? That doesn't make sense."

Makes LOT of sense, higher speed or driving at speed of rest of the traffic will require hard braking(>6m/h in 1sec) and turning.

Most insurance companies also seem to be offering these dongles which rate you based on your driving. What doesn't make sense is person can be "aggressive driver" without considering type and condition of their car. A performance car(BMW, Porsche etc.,) will be able to slow down or turn faster while being more safer than any CUV/SUV.

[jdlshore]

I don’t see how higher speed equates to hard braking and turning. I regularly drive 75mph on the I-5 in Washington (state) and never have to hard brake or turn. It’s just a matter of not following too closely—I aim for about 2s following distance myself, a number that was impressed upon me as a teen in Driver’s Ed.

[Traster]

If I drive slowly the likelihood of spotting a forward collision early is higher and I have more time to react, and certainly the speed differential as I approach some stopped traffic is lower reducing my braking intensity. If I'm driving slower I can make the same radius turn with lower Gs improving that rating, and I'm also going to be much more likely to be following safely since at the lower speed I can be closer whilst still having a safe headway.

So basically every metric is easy to improve by simply driving slower.

[ReidZB]

That's assuming you're varying only speed and not e.g. following distance. I try to leave at least 3 seconds' distance pretty much always (often more), so I have a pretty consistent amount of time to react regardless if I'm driving 30 mph or 55 mph.

Additionally, most of the metrics are cut-offs. It doesn't matter if you brake very gradually or if you brake very close to the area where it penalizes you. Based on my driving so far, the hard braking threshold is pretty forgiving. Yesterday, I let off the accelerator completely and went full-regen braking and it didn't care.

Anyway, I've driven 99 miles (highway/city mix) with the Safety Score thing turned on, and I'm still at score 100. I haven't slowed down at all.

[tim333]

I don't know what criteria they use for unsafe follow time but I remember a government suggestion that was pretty impractical for rush hour motorway type driving. There were just too many cars packed into the road space to spread them out that much so even good drivers end up close to the vehicle in front.