The Automobility unofficial port has a new public beta for Minecraft 26.1.2 and 26.2, with a clearer distinction between braking and reversing.
Hold S to brake. Once the car stops, keeping S held keeps it stopped. Release the key and press it again when you want to reverse. The same rule applies with or without Momentum.
The release also brings the vehicle synchronization and driving corrections used by the matching Pumps & Pistons integration. For the new fuel setup, use P&P 1.10.4-beta.1 and Automobility 1.0.0-beta.1; add matching Momentum 1.0.0-beta.1 if you want it.
P&P and Momentum remain optional. Update your chosen gameplay mods together on server and clients, using files for the same Minecraft version. These new beta files target 26.1.2 and 26.2; they do not replace the separate existing 26.3 downloads.
This is an unofficial port, independent of the upstream Automobility project.