Semis specs vary a lot, even for long distance trucks. Hills require a lot of torque. Owner operators make configuration trade offs between speed and fuel efficiency. Braking is complicated with EV semi. Engine braking is replaced by regen, and definitely improved over a diesel truck. But trailer braking will just be standard brakes. Maximum regen only braking has the risk of fishtailing the trailer. Since Tesla likely won't deliver a semi before 2020, they can announce a truck based on battery and charging technology that isn't in production yet.