@Science fan , but they are not limiting on a divided highway or limiting the TACC on either divided/non-divided so I really don't buy that excuse at all.
You can't compare TACC...that's effectively a smart cruise control and no different than any other car cruise control. With respect to autosteering, there is a very big difference between a divided, limited access highway and other roads. If nothing else, on a divided, limited access highway:
- The possibility of dealing with opposite direction traffic is non-existant
- The possibility of dealing with crossing traffic is non-existant
- Newly merging traffic is doing about the speed limit
Even on a divided, non-limited access road (i.e., a road with islands between the two directions as some have mentioned in this threat, 2 of those 3 things are not true. As a result, it may be reasonable to assume Tesla has determined that doing in excess of the speed limit on a non-divided/non-limited access road may create a condition where the auto-steer/autopilot capability cannot recognize and deal withe the situation in time when going over the speed limit.
For example, let's say that there is a non-divided, non-limited access road -- say the two lane country highway such as in rural areas. Many of these have intersections where a road crosses perpendicularly...there isn't a light -- just the perpendicular traffic has a stop sign and is supposed to yield to the highway traffic when crossing the highway or pulling on to it. In these cases, there is the possibility that a car might merge in front of you doing 15 or 20 miles an hour when the speed limit is 55 or 60. Obviously that car is accelerating and (hopefully) the driver did not pull out in front of you if there was insufficient room for him to accelerate to highway speed, but people tend to do stupid things. It may be that Tesla determined their system could recognize this and brake to a stop (or at least slow down enough) to avoid a collision, bu that if you are doing over the speed limit, there simply isn't enough time because the maximum detection range of the AP 1.0 sensors simply doesn't permit the AP system enough time to (a) detect the vehicle, (b) process the situation and (c) take action to avoid a collision. Now if you have TACC engaged and are doing 90 mph for some reason, it is on you to recognize the issue and stop. With AP engaged, you have an expectation that the AP isn't going to drive you into a collision.
I agree that there are legal and regulatory issues here (do you allow an AP to speed and "break the law"?), but it is entirely reasonable to assume that Tesla has concluded that a sufficient safety margin cannot be achieved on non-divided, non-limited access roads if the car is speeding. At the end of the day, I think that there are three things that will drive what speed Tesla will let you operate at in autopilot mode:
1. The law (speed limit)
2. Federal guidelines/regulations on use of autopilot (these are still in development as the technology develops but right now effectively say "no speeding")
3. The technical ability of the system to identify issues and address them which is a function of:
a. the range of sensors
b. the processing time of the system
c. the potential closure rate
(a, b and c all effectively constitute "reaction time").
Because a non-divided/non-limited access road creates the potential for a greater speed differential between the Tesla (or any autopilot vehicle) and conflicting traffic, closure rate is potentially greater and thus reaction time decreased given 3a and 3b are constants.
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