Welcome to Britain's most magnificent jam

THE RIPPLE of brake lights down the stream of traffic signals the start of another day of tailbacks and frayed tempers at the most congested traffic blackspot in Europe. By midnight, 160,000 motorists will have crawled past the M6/M5 intersection, near Birmingham in the West Midlands. This is double the number of vehicles the road was designed to carry.

For drivers, the intersection is a canker at the heart of Britain's overloaded motorway network. For motoring organisations like the AA and the RAC, it is the snarl-up that never ends. The police who patrol the motorway have to deal with more than 100 incidents in a typical day. The slightest problem, such as debris on the overloaded carriageway, is enough to upset the road's delicate equilibrium and bring miles of traffic to a standstill. The only lull comes between midnight and the early hours. Then it all starts again.

The latest quarterly figures, released last week by the Department of Transport, show that traffic growth is showing no signs of slowing. The number of vehicles on Britain's motorways has increased by 2 per cent in a year. A survey by Lex Vehicle Leasing shows congestion is costing business pounds 4.5bn a year.

Sgt Barry Mason, of the Central Motorway Police Group, is relaxed. Today he regards the traffic as light, although six miles of tailback would be described as hell by the average motorist.

It is just after 9am and the illuminated motorway boards are still flashing. They warn drivers to slow to 30 mph as they approach the "crossroads of the country", as the notorious intersection is known. The signs are often left flashing through the day when, as is frequently the case, the rush-hour chaos leaves a legacy of tailbacks.

On the northbound carriageway, the traffic is crawling, as the five lanes of the M6 merge into three. Southbound, the faces of drivers are contorted by frustration as they weave across the carriageway to claim places in the proper lane.

The intersection and the M6 itself are victims of their own design. Built 24 years ago, the motorway is chronically overloaded, but it cannot be widened to meet the increasing traffic demands because it is elevated in many places.

The M6 here also has more junctions, which slow the traffic flow, than a rural motorway. In one 15-mile stretch there are eight junctions.

A relief road is being planned to take traffic off the motorway and there has been an experiment to use the hard shoulder as an extra lane. In the meantime, motorists must tolerate the congestion.

The stretch of road to the intersection has seen more than its fair share of tragedy. Last year, three people died in a 160-car pile-up, in thick fog - the biggest motorway accident in this country. The heat from burning cars melted the road surface. In another incident, a tanker shed part of its load of 22 tons of cows' blood. There were fears that it was contaminated with BSE, and the carriageway was closed for nearly a day while it was cleaned up.

The economic importance of the motorway also makes it a target for terrorists. The IRA once left a bomb under the concrete carriageway supports, a few miles north of the infamous intersection. The motorway was closed for several days, and freight companies lost millions of pounds in business.

"You can go for days without anything but when something does happen it can be huge because of the volume of traffic," said Sgt Mason. After 10 years patrolling the M6, he confesses to having developed a deep affection for this stretch of the motorway, despite its bad reputation. "It is a unique world and you develop a very territorial attitude towards the road, like a sailor getting attached to his ship," he said. "All the police who work here are very proud and fond of the road. The environment can be very hostile so safety is paramount, but it can also be very pretty sitting here in traffic. The hard-core commuters learn to build their lives around it rather than battling against the delays."

In the control room, the crew has been busily directing officers to breakdowns, minor accidents and oversized vehicles, and a report of "a kitchen unit on the carriageway".

Sgt Peter Williams started the day with a step ladder in lane three, just in time for the start of the rush hour. Later he has to activate the debris warning again when a piece of tarpaulin lands on the M6. Another day, it could be swans mistaking the wet road for a river, or people mistaking the road for a crossing. By lunchtime, there have been 18 incidents played out on a bank of monitors in the control room. They sit alongside a map of the motorway system which resembles the cross-section of an ants' nest. Out on the rain-spattered carriageway, the traffic is building again. Most of the drivers are oblivious to the striking backdrop of smoking chimney stacks, the gaily coloured flags of the Ikea store and the space- age architecture of the RAC traffic centre.

By 5pm, the variable message sign is warning of "Delays M6 North" and the tailback is stretching to junction 10. The lorries and company cars cramming the length of the road are stationary and businessmen are forced to stare at the grubby backsides of Nissan trucks. For many, dinner will be cold by the time they reach home.