The transport police chief in Iran's capital added his voice on Tuesday to criticism about the city's interminable traffic jams, the bane of almost every Tehrani's existence.

"We have reached a point where the traffic has become unbearable. It can no longer be tolerated," said Mohammad Reza Mehmandar, according to the ISNA news agency.

"This situation is because of years of inattention. We must find a solution now."

As the city's population has grown to some 14 million in recent years, swallowing up outlying villages and attracting millions of new workers from the countryside, Tehran's roads have failed to cope.

Commutes have become a waking nightmare in which it can easily take several hours to drive a short distance.

On one recent evening ahead of the holiday marking the death of the Prophet Mohammed, the rush to get out of town meant commuters in north Tehran took more than five hours to travel just four kilometres (2.5 miles).

There are around five million cars on Tehran's streets -- many of them battered old models that spew noxious gases and turn the roads into a respiratory hell.

And the city's 3.5 million motorbikes are often even more polluting than the cars.

Mehmandar bemoaned the fact that two-thirds of the cars on the road at peak hours had only one occupant, with congestion particularly problematic in the rich north of the city, where he said people use their cars for any little outing.

Even the construction of more than 100 metro stops has had minimal impact.

Mehmandar said measures that limit traffic, such as alternating which cars are allowed to circulate based on their number plates, should be extended to more of the city.

But there seems to be no easy solution to the problem, not least because the lack of careful planning has created endless bottlenecks around the city.

There have been desperate measures -- such as building flyovers over existing flyovers -- but the roads have quickly become clogged with fresh traffic in a city that registers around 1,000 new vehicles a day.