According to several studies, each $1B of construction costs for highways uses 10 trillion BTUs of energy. One gallon of gasoline contains about 125,000 BTUs of energy.
A quick calculation shows that $8.4B of highway construction will use the equivalent of 670,000,000 gallons of gasoline. Using our earlier estimate of 10,000 vehicles per day of which 5,000 are passenger cars and 5,000 are heavy trucks, the Bypass would save 25,000 gallons per day. That is based on cars getting an average of 25 mpg and trucks 5 mpg, and the highway being 25 miles shorter than the current route.