Folks, we really REALLY need to get past this whole "L maximizes regen" misconception. It maximizes nothing. When you take your foot off the long pedal in D, the Volt applies the regen brakes a little bit and you slow down slowly. When you take your foot off the long pedal in L, the Volt applies the regen brakes harder, and you slow down a little faster. The amount of energy recovered doing that from 30 to 4 MPH either way is basically the same, because that's how physics works. E = (m)(v1-v2). The same thing applies to the brake pedal. Unless you're panic-braking, 30 to 4 MPH still regenerates the same as L or D.
(And you're not regenerating, even in a Bolt, below 3-4 MPH. That last stopping is USING energy from the battery to slow the car, not giving it back (either by reverse torque or applying the friction brakes for you. I don't know for sure which, but I suspect the former). It only does that because people think "One-pedal driving is cool".)