Major accidents in Maryland and the District of Columbia produce steadily fewer fatalities. Do we know why and can we keep it up?

We routinely discuss major car and truck accidents in Prince George's County and the surrounding counties of Maryland. Consequently, one might reach the conclusion that vehicle crash deaths are on the rise, when in fact the opposite is true both locally and nationally. http://www.maryland-law.com/blog/crash-deaths-reach-sixty-year-low.cfm

The inevitable question is why? The answers posited by a recent NHTSA study are somewhat unsatisfying as an explanation but focuses on specific groups who have reduced their fatality rates, resulting in safer roadways. http://www-nrd.nhtsa.dot.gov/Pubs/811346.pdf 

The reduction in crash deaths that have profoundly effected the overall yearly crash death totals nationally are in the following populations: young drivers and their passengers ages 16 to 24, passengers 15 and under multi-vehicle collision victims and weekend drivers.

One can appreciate that reduced crash fatalities among young people would have a significant impact overall as they are more accident prone than their elders, but why are they having fewer deadly crashes? http://www.maryland-law.com/blog/maryland-highway-safety-office-focuses-on-young-drivers-and-crash-avoidance.cfm

NHTSA suggest that wider prevalence of crash avoidance programs and greater crashworthiness of vehicles along with increased rates of youth unemployment are major factors. One can understand that if cars are safer and young drivers are better trained in driver's educational programs in crash avoidance, this would have a very positive effect but what does  youth unemployment have to do with it?

The answer one supposes is that younger drivers are not only less apt to be on the roadways going to work but also that the absence of wages means that young drivers are not out on roads spending their hard earned pay recreationally. This correlates with data that reflects that periods of recession see fewer vehicle miles driven overall with concomitant reductions in vehicle crash deaths.

The question is will the return of the American economy mean more crash deaths again or will the same factors that reduced the incidence of youth crash fatalities, more crashworthy cars and more emphasis on crash avoidance, save the driving population as a whole?