There are two primary reasons to introduce bus service into Kabul (or anywhere).
One is to reduce the need for cars in the city. There is the hope that the presence of public transportation (in this case, a regulated, structured, and defined public transport as opposed to the entrepreneurial and chaotic) will encourage people to leave their cars behind. This is a vain hope. Cars are pouring into the country and the city and people want to drive. No bus system is going to be more than a drop in the ocean.
The second is to provide transportation for people too poor to afford other modes of transport. This is definitely a valid concern in a country as poor as Afghanistan and a city like Kabul, which is drawing in the poor and jobless from the countryside. But they'll still be stuck in traffic.
If a donor really wants to help Kabul take steps to deal with its traffic, there are better ways than introducing more vehicles onto the roads. First, rehabilitate and expand the system of traffic signals; some intersections have lights, but none of them appear to be functioning. Second, invest in drivers' education. Third, make the licensing process more rigorous (in other words, establish a licensing process in which people actually participate). The municipality is taking steps toward this (they've stopped giving out taxi licenses, for example), but so far there has been no noticeable impact.
Can't wait to see the city in five years.
Posted by Martial