"Did you notice that, of the 32 provinces, they have data from only eight? It's not because those eight are viewed as representative, either. It's because those are the only eight provinces where it's relatively safe for those administering the questionnaires and conducting the interviews to travel around."

Did you know that the roads in Afghanistan were in poor condition.
Have you ever driven at say 50 mph on roads which as in as poor condition as those found in Afghanistan? Probably not. Even well maintained gravel roads which are not dead flat and straight are hard to travel at 50 mph or higher- and Afghanistan isn't known as a flat plain- some say it's got a few mountains.
America has huge amount of paved roads- and a small amount of unpaved roads. I vaquely recall some stat that America had something like 18,000 miles of paved road. Oh screw it; I will google: America has 2,425,000 miles of paved roads [only factor of 100 or so off:)
While looking, some other facts:
"
"Kabul, February 11, 2004 -- The U.S. Ambassador to Afghanistan and Special Presidential Envoy Zalmay Khalilzad, together with President Hamid Karzai, today announced plans to begin construction of over1,300 kilometers (812 miles) of provincial roads in Afghanistan. These roads are key to Afghanistan's future and are a powerful indication of the country's continuing recovery from years of war and isolation.
...
The construction of these roads is an important step in the continuing normalization of life in Afghanistan. Years of conflict have devastated Afghanistan's infrastructure - particularly its roads. The absence of a viable road system has left many rural areas isolated and beyond the reach of the central government."
http://usembassy.state.gov/islamabad/wwwh04021102.html

"Soviet tactics utilized the following military and economic efforts.
...
More than 20 million anti-personnel mines were dropped by the Soviet Union. Some of these anti-personnel mines were shaped like pens, or dolls, or other shiny trinkets, known as 'dolly bombs', intended for children to attempt to pick up.
...
70% of paved roads destroyed. "
http://www.campusprogram.com/reference/en/wikipedia/s/so/soviet_invasion_of_afghanistan.html

"We will help it reach its goals – such as a doubling of the percentage of paved roads in six years – by completing the Kandahar-Herat highway, and by supporting the efforts of international bodies to complete, by the end of 2004, roads they are constructing."
http://66.102.7.104/search?q=cache:r6PjovhRT8gJ:www.ustreas.gov/press/releases/reports/action_plan_on_afghanistan_final.pdf+%22Paved+Roads%22+%2B+Afghanistan&hl=en

Anyhow, I didn't find the exact numbers as for amount paved and unpaved roads in Afghanistan. But there isn't much paved roads [we are doubling it- and still it won't be much]. The point is that traveling by road in Afghanistan would be a bitch- without considering theives or terrorists- just pitting you against the roads [oh, and don't even imagine there is some kind of gas station every 100 miles].
So, if not road, that leaves air transport- there is 8 airports in Afghanistan- count them your self:
http://www.afghana.com/Map/MapRoadsAirports.htm
Oops, there is 9 including the one in Kabul.