NAIROBI, Sep 25 (Reuters) Once known as East Africa's green ''City in the Sun'', Nairobi is so choked with traffic that Kenya's architects suggest moving to a new capital and angry business leaders say the booming economy is under threat.
A combination of bad drivers, ramshackle vehicles, overloaded trucks, potholed roads and corrupt traffic police make one of Africa's biggest cities resemble the dodgems on a good day and, when things get really bad, reduce it to gridlock.
Swarming minibuses, known as matatus, are the only option for most Nairobi commuters, but they are notorious for their drivers' kamikaze tactics and their crumbling mechanical condition - which often means no lights at night.
Matatus, weaving wildly from lane to lane, account for 80 percent of public transport and are a major cause of congestion.
Fatal crashes are common. The Sunday Nation newspaper called a recent spate of matatu accidents a ''national slaughter.'' Kenya's crumbling roads and the chaotic traffic have become a political issue ahead of elections in December, denting the popularity of President Mwai Kibaki.
A recent survey said traffic jams were costing Nairobi drivers up to 50 million shillings (746,000 dollars) a day through increased fuel consumption, mechanical damage and pollution.
''The amount of fuel used is astronomical, just sitting in traffic idling away, '' said Betty Maina, head of the Kenya Association of Manufacturers.
''Things are delayed, you don't accomplish as much, it takes longer getting to meetings and events. You get up earlier trying to beat the traffic but sometimes you just cannot beat it.'' She said the turnaround time for trucks and vans had doubled and some companies were increasing the sizes of their delivery vehicles because of the delays, compounding the problem.
SHIFT CAPITAL? The Architectural Association of Kenya (AAK) last month asked the government to move the capital elsewhere.
''Nairobi was designed half a century ago for a population of half a million people while the population today is three million. This has overstretched entirely all the services of the whole city,'' AAK chairman Gideon Mulyungi said in a speech.
City traffic is worst on Friday evenings, especially near pay day. When rain turns the potholes into ponds, there is chaos.
The jams are regularly compounded by a string of accidents and breakdowns, many involving ancient trucks which have a tendency to roll backwards down Nairobi's many hills.
Nairobi's traffic lights are largely ignored.
The police, known for being more interested in bribes from harassed motorists than untangling the jams, often overrule the lights anyway and their efforts can make the hold-ups worse.
Yet experts, including Japanese road engineers who did a two-year study, say Nairobi's problems are not insurmountable and nothing like as complex as some cities.
While traffic has expanded - some estimates say by 300 percent in a decade - the roads have not.
''The problem is the growth of vehicles compared to the rate of developing the road network. For some time this has not been developing while traffic expanded,'' City Engineer Charles Chiruri said.
There is only one road, the Uhuru Highway, running right through the city and it is punctuated by a string of roundabouts acting as anarchic traffic traps.
The highway is used not only by most commuters but also by heavy trucks transiting to all parts of the country, including from the port of Mombasa to Uganda and central Africa.
''MISSING LINKS'' Plans to overcome Nairobi's congestion - bypasses, overpasses and 14 ''missing links'' to avoid long detours - began 30 years ago. Nothing was done.
The reason, say experts, was systematic corruption during the 24-year rule of former President Daniel arap Moi, who was replaced in 2002 by Kibaki.
For the decade after 1994, foreign donor funding, essential for building new roads, dried up because of the huge graft.
''By 2002, things were so bad that what was happening was there was no competitive tendering at all. Just a cartel of five cowboy contractors,'' said a former government engineer who asked not to be named.
''They quoted whatever they liked and then doubled or tripled it. They got paid and did not do the job and then claimed more because of bad weather.'' By the end of the Moi era only 20 per cent of the country's roads were in adequate condition.
It is taking years to overcome the backlog. Even now, five years later, about 57 per cent of the network is in poor shape, while the booming economy puts even more cars on the road.
Big donor countries privately express frustration that the comprehensive 2006 Japanese plan for solving Nairobi's road and traffic problems has still not been implemented.
Roads Ministry spokesman Richard Abura said it had taken time to find donors to fund the work. ''Early this year we started implementing the report. We are going to concession the bypasses as soon as we get some funding.'' In April, President Kibaki announced plans for a 2 billion Kenyan shilling (30 million dollars) Chinese project to widen the Uhuru Highway and link it to the west of the city.
But some Western donors complain this is not coordinated with the Japanese plan and many people remain sceptical at the pace of change.
''I don't think this is going to improve in the short term.
The issue with Nairobi is that there just isn't a comprehensive plan in place yet,'' said Maina of the manufacturers' association.
REUTERS ARB KP0852