More than seven years after the fall of the Taliban, the streets of Kabul are gridlocked with cars, many of them so rickety they failed roadworthy tests at home and were shipped off to Afghanistan instead.

Importing vehicles into Afghanistan has become one of the most lucrative businesses in the country as vast injections of foreign cash help the economy recover from years of civil war followed by austerity and sanctions during the Taliban era.

But unscrupulous traders are exploiting a lack of import regulations to ship in vehicles that fail safety tests in other countries, officials and dealers say.

"Afghan traders mostly import Japanese Toyota cars that are second-hand and salvaged," said Amir Mohammad, a police officer in charge of Kabul's crowded city centre.

Some 90 per cent of used cars were bought in Germany and Canada and then shipped to Afghanistan via Dubai and an overland route from Iran.

Businessmen and high-ranking officials drive Toyota land cruisers and Lexus jeeps. Other cars are out-dated, with Russian taxis from the 1960s and 1970s still creeping through the city's streets, clogging the capital's skies with pollution.

The government, about two years ago, restricted importing vehicles more than a decade old, but then abandoned the rule in the face of protests from traders who said they had placed orders for old cars and Afghans could not afford newer models.

"There is no law that stipulates what type and what models of vehicles the traders can bring in," said Finance Ministry spokesman Aziz Shams.

New cars anyway have a mixed attraction, in a country where crime, guns and violence are still rampant.

"Most people don't want to buy new cars because it attracts the kidnappers and robbers," said civil servant Nadir Shah.

"On the other hand, most cars on the Afghan roads are very old, they might have had dozens of accidents before getting to our country," he added.

The average profit on a salvaged car is around €746 and business is booming, with an average 20 cars per day sold in Kabul alone, dealers said. Prices range from about €3,000 for a 1996 model to €12,000 for a 2006 Toyota Corolla.

There are also thousands of cars brought in during the early 1990s that had the steering column crudely, and dangerously, modified to fit Afghanistan's right-hand drive road system.

The largely narrow, unpaved and pot-holed roads of the city are now flooded with 400,000 mostly second-hand cars, nearly ten times the amount they were originally designed for.

"Kabul was built for a population of half a million and an estimated 50,000 cars," said police officer Mohammad, who did not give his full name.

"Since the increase of people and cars in the country, the government has not done anything major to provide comfortable, good lives for the capital's citizens."

The city is surrounded by mountains that once made it cool and beautiful, but now serve as a trap for pollution. Their slopes are speckled with illegal shanty homes thrown up by recent arrivals who have nowhere else to go.

Kabul's population is now nearly five million, and its air is so dirty that an estimated 3,000 people die from pollution-induced illnesses each year, environment officials say.

"Old cars make up one of the biggest problems, and are the source of much of the pollution," said Dad Mohammad Baheer, deputy director of the National Environment Protection Agency.

The traffic department in the capital registers some 9,000 old cars every month, he added, and the crumbling city infrastructure adds to the problem.

Road-building in Afghanistan is a notoriously corrupt business, and the cheap workmanship that results can rarely withstand the country's extreme weather.

"Cars travelling along the filthy, and mostly unpaved Kabul roads throw up large amounts of dust which is very harmful for the public," Mr Baheer added.

Environmentalists hope the government will make good on promises to revive the regulation banning imports of old cars.

But even if it is pushed through and car and air quality improves, the capital's residents are unlikely to see a quick end to long, frustrating commutes down over-crowded roads.

"There has been no balance in car importing and road building," said finance ministry spokesman Mr Shams.