An electric assist vehicle is described, which may have a cargo area, a drivetrain including an external crankset and an electric motor, and a speed control system. The speed control system automatically limits the maximum operating speed of the vehicle based, at least in part, on a load mass (e.g., a gross weight) of the vehicle and/or the cargo area of the vehicle. Limiting the speed includes, for example, reducing the power of the electric motor and/or increasing a braking force on the vehicle.