One of the advantages of Electric Buses over Streetcars was the ability to move from one lane of traffic to another. The same can be true of Electrified over the road trucks. Now you may say why not a Hybrid/Battery system? The reason is simple, with a direct wire system you do NOT need Batteries thus the overall vehicle is lighter AND as long as you are on Wire you have power i.e. no need to recharge.
Here are some pictures Trucks propelled by overhead electric wire:
Other sources for information on Trolley-trucks:
http://en.wikipedia.org/wiki/Trolleytruckhttp://www.google.com/images?hl=en&q=Trolley+Truck&um=1&ie=UTF-8&source=univ&ei=LovRTL7yKYS8lQeZvOy3Dg&sa=X&oi=image_result_group&ct=title&resnum=4&ved=0CEAQsAQwAw&biw=1152&bih=630http://hutnyak.com/Trolley/trolleyhistory.html#BarrickAm Article advocating overhead power for Trucks:
http://searchwarp.com/swa358504.htmTrolley-Buses and Trolley-trucks (both powered by overhead electric wire) have several advantages:
1. As a vehicle, being electric driven, the life span is two to three times as long as a diesel operated vehicle (This they share with Conventional Streetcars/Trams/Trolleys/Light Rail Vehicles, hereafter referred to a LRVs)
2. On hill climbs more power can be provided to the wheels then in a Diesel with the same size engine (Again an advantage they share with LRVs)
4. On a Hill climb have the traction of a rubber tired bus (An advantage such Trolley-Buses and Trolley-trucks have over LRVs, but at the cost of having to use more power to overcome the increase friction do to the increase traction, thus except on steep hillsides, i.e more then 15% grade, not worth it, but on grades over 15% an distinct advantage for the Trolley-bus/Trolley Truck).
5. The ability to switch lanes, even if only one lane has overhead wires (an advantage over LRVs, but of limited usefulness in real life).
6. The need only to maintain the overhead wire NOT the tracks. The main reason trolley-buses came into use starting in the 1920s, replacing LRVs (generally called Trolleys or Streetcars then). The early LRVs saw that by going to Trackless Trolleys the line no longer had to maintain the road in addition to the tracks (And common franchise requirement) and thus save the cost of maintaining the road be in addition to the tracks.
7. Electric Power was cheaper then diesel (an advantage trolley-Buses/Trolley Trucks share with LRVs).
The big DISADVANTAGE of Trolley-Buses is the need to two sets of overhear wires. In LRVs power comes from the overhead wire and the return electric line is one or both of the electric rails. With a Trolley-bus you can NOT do that, thus you must have TWO WIRE, one for power, the other the return. Remember all electricity MUST have a return to where the electricity is produced. Thus the need for two sets of Wires when Trolley-Trucks are being discusses (But only one set of wire on LRVs, do to the return via the rails).
The problem was that the cost of most mass transit is dominated by LABOR Costs NOT energy Costs, About 80% of the cost of providing transit is the cost of labor NOT Diesel or Electricity. Thus Labor Cost was and is an important consideration of any transit system, often more important then what the transit system uses as a source of Energy.
Getting funding for such Electric driven system was the second major problem in the late 1940s and into the 1950s (When a lot of transit system needed to upgrade their equipment, much of it NOT upgraded since the 1920s and by the late 1940s is disparate need of repair). GM was willing to provide funding for buses it made, but nothing else. The Makers of Electric LRVs and Trolley-Buses did NOT have the ability to provide the loans needed to buy their products and most banks were NOT willing to provide the funding either. Thus access on how to pay for what was to replace the 1910-1930 purchased equipment also drove transit away from Electricity and to Diesel.
Anyway, the need for funding since the 1960s has been provided by the Federal Government more then private banks, thus no longer a major concern, but the problem of labor remains.
On the other hand, the advantages of electric overhead wire even for over the road trucking is clear. Whole new trucks would have to be produced and a way to charge the truck for the electric power their use, but with modern computers not much of a problem. Thus electrification of the interstate might be a better Carbon reduction program then the Electrification of the Rail System.