Breaking Down Braking's Problems

In the average 600 miles journey the driver of a heavy transport tractor trailer will make at least 1000 gear changes. Experienced drivers estimate that a third of any trip is spent braking! Since every gear change brings wasted fuel and engine wear, and all that braking is just wasted energy and break wear, there are huge opportunities in putting the energy to better use. The descendants of Vince Carman's ill-fated dream may be part of the solution...Borrowing from the hydraulic transmission principle, hydraulic assist braking systems sit in between the engine and driveshaft, allowing slowing of speeding up of the wheels depending on the situation. When the trucker applies brakes, the crankshaft turns a pump which pressurizes hydraulic fluid in an accumulator, and slowing the wheels, which reduces the amount of brake pressure needed to stop the truck. Now, when the driver wants to accelerate, that stored pressure is used to spin up the crankshaft, relieving the burden on the engine, which is running at a horribly sub-optimum RPM, and burning lots of extra fuel. With the assistance, the driver can start in a higher gear, and use less fuel.

The benefits of this system over a fully hydraulic drivetrain are its potential for retrofitting into existing trucks, and its lower upkeep costs, since it can be mostly sealed and self contained. An added benefit for everyone is the increased stopping power of the trucks, which leads to better road safety. These systems are under development for commuter and cargo trains, and garbage collection vehicles, in addition to cargo trucks

Multiple companies, including Permo-drive, and Shep technologies are working on these technologies, so chances for their implementation seem better than ever (or at least better than 1970).
Thanks to Wojciech Sierka for the tip. [by DM]