I have mixed feelings about Pro Pilot after 16 months of driving the 2019. I thought it did a good job of keeping the car in the center of the lane even with faded lane markers when I experimented with it the first few months, but now it crowds the center line, seems to be sluggish in steering, and drops out more frequently. In thinking back, some of the difference may be due to changing the tires. The Bridgestone DriveGuard run flat tires have stiffer sidewalls and a stronger on-center feel so it takes more effort to initiate turns (which gives the driver a better feel of the road). The self steering may be optimized for the OEM tires which take very little effort to initiate direction changes.
One thing I noticed even when new is that the system is confused by dips in the road. Many of the roads around Phoenix have dips when the road crosses normally dry washes because it is not feasible to install culverts large enough to handle flash floods. If I let Pro Pilot do the steering on these roads, the car will drift to one side when going down into the dip, overcorrect, and drift to the other side when climbing out the other side. If there is no oncoming traffic, I let it go and it will cross the centerline or shoulder stripe before it corrects itself.
