[energywut]

Yes. The energy in a vehicle increases with the square of the velocity. A car going 40 has nearly DOUBLE the kinetic energy of a car going 30 and the braking time required to stop a car is therefore also significantly increased.

That lower speed limit was set for a reason.

Additionally, predictable car movement is important for wildlife, pedestrians, and other vehicles. If the cars on that street always go 30, the others there will learn to predict the movement of a car. If some rando car start speeding along at 40 out of the blue, that will disrupt the calculations and decision making of everyone else.

Finally, are we comfortable saying, "Any company can decide whether it thinks obeying the speed limit is important, and is free to go over the speed limit by 1/3rd if they deem it safe"? Are we sure that precedent is healthy and desirable? I'm not. I don't think automated cars should just decide to add 33% to a speed limit and go that fast in normal operating conditions.

So yes, it does matter.