Drove four hours worth of northern New Hampshire and Vermont interstate today and it was my first chance to significantly try out the autopilot.
It is definitely beta. What I found driving at the speed limit in the right hand lane the whole way was that the issue described in this thread subject depends on the specific lane markings for each exit. About 70% of the exits had the solid white right line curve away following the exit, and no markings across the middle of the new exit lane, then, on the far side of the exit lane, there were new white solid lines starting in a v with one part being the left line of the new exit lane and the other part being the continuation of the interstate right lane's right side line. In every occurrence of this configuration, the autopilot attempted to take the exit, regardless of whether there was a car in sight in the lane ahead of me or not. The only variant of this configuration I wasn't able to test was closely following a car because they were generally going faster than the speed limit.
The other exit configuration, which I saw about 30% of the time was mostly the same, but with a small dotted line crossing through the new exit lane and continuing the interstate right hand lane right line marking until it met up with the new solid white line after the exit. In this configuration, the car sometimes hesitated a bit, but it was always able to keep to the right hand lane and continue travelling straight.
One experiment I tried that successfully kept it in lane when passing an exit without the dashed right side line was to turn on the left turn signal for a moment just as the right side line curved away toward the exit. This caused the car to stay toward the left side of the right lane in preparation for changing lanes. This method did not work if there was a car to my left that would prevent starting a lane change, and if I was too close to the left lane marking or if I held the turn signal too long and the car began to exit my current lane toward the left one (i.e. it crossed the line) this method resulted in either fully changing lanes to the left or in the car jerking back into the right lane or giving up entirely and cancelling autopilot. When I timed it correctly though, it was slightly better than just stiff-arming the autopilot to avoid the exit then re-enabling it once the exit was past.
I consider this to be the biggest failing of autopilot so far, and if I were making the call, I would not have wanted to release it as beta with this particular flaw. This is interstate driving in clear weather and good lane markings. It should not be forcing the driver to wrestle or disable it every mile as the next exit comes up.
I also feel it has a pretty straightforward solution. The autopilot should prioritize the left lane marking over the right lane marking, especially when it can tell it is in the right-most lane, and especially if it detects the lane is suddenly getting wider.
Vice-versa, when it can detect it is in the left most lane it should probably prioritize the right side line to avoid following left exits.
The challenge is a one lane interstate with exits on either side. In this case, I imagine it might be able to rely on "connecting the dots" by trying to see if the lane is widening, trying to see if there is a v continuation of the solid line further ahead, relying on map data to determine if there is an exit here.
At the very least, letting the driver nudge it into staying straight without having to wrestle the autopilot off then re-enable it two seconds later would be a much better user experience.
