I thought a lot about reducing truck energy usage. The basic problem is for any real reduction (greater than 10%) of trucking fuel demand, it would take a long time to happen.

The problem is they have already tried a lot of energy reduction. When a 300 gallon tank costs $1200, they think of what they can to reduce that price. Speaking with truck drivers, they don't have options when it comes to reducing fuel use. The best one is driving slower, which will move some of them from 6.5 mpg to 7 mpg. However, it would reduce the amount of freight a trucker could deliver and thus the profit. It is not a very good option for them. Even if it did happen, it would only drop highway truck consumption by ~5% (going from 75 to 55) and less freight would be delivered.

When it comes to replacing trucks with hybrid versions, there are a few problems. Hybrid trucks are really expensive ( 100k or more than a same model diesel ), don't save much fuel (0% highway, 10-20% city) so they are not cost effective. Also, there really aren't many on the market. Full battery electrics are not feasible with todays technology, not an option.

On the flip side, nearly 50% more of us could take a bus/subway or ride a bike to work 3 out of 5 days a week. 10% more of us could telecommute 3 out of 5 days a week. 75% of the SUV's and trucks on the road could be replaced by economy cars (yes I know, this would take a long time, and is unlikely). We could be moved to the 4 day work week. On top of that, there are many (15+ models from major manufactures) PHEV and EV's coming onto the market within the next 5 years (and yes I drove one, they are good commuters).

Bottom line, within 5 Years, I believe that gasoline demand could drop by 25%, easily. However, diesel demand would be struggling to drop by 10%. There are just way more alternative to gasoline than there are to diesel.