High fuel costs and environmental considerations are forcing both businesses and individual travellers to re-evaluate their travel habits.

A study released earlier this week by navigation specialist Trafficmaster, says congestion on UK roads fell by 12 per cent in the first six months of this year, compared with the January to June 2007 period.

Experts say a significant cause is less business travel, with commuters and executive travellers eschewing roads and air in favour of rail and web conferencing technologies.

Although car hire firms' profits have so far remained steady, some companies are warning that profits may be hit by business customers wary of fuel costs.

Discussing the results earlier this month, Avis chief executive Ronald L Nelson admitted that "the impact of rising fuel costs and a weaker economy began to affect travel volumes in the second quarter".

A week later Hertz chief executive Mark Frissora said on a conference call: "The second quarter was indeed a challenging one for the rental industry. We have a difficult economic environment."

However, a spokesman for the British Vehicle Rental and Leasing Association (BVRLA) said it was not overly concerned the industry was losing business customers. "Our members are reasonably positive," he said. "Europcar saw an 18 per cent increase in bookings over the summer compared to last year."

The BVRLA was unable to say how many of these were business bookings, but said that on average 60 per cent of car rental firms' bookings came from business customers.

Airlines are also suffering from a lack of business trade, which combined with high fuel costs has caused serious problems for many carriers.

Earlier this month, the International Air Travel Association (IATA) released figures showing the slowest growth in European passenger volumes since the industry was hit by the SARS crisis in 2003.

"With consumer and business confidence falling and sky-high oil prices, the situation will get a lot worse," said Giovanni Bisignani, director general of IATA.

Twenty-five air carriers have declared bankruptcies so far this year, including all-business class airline Silverjet which operated routes to the United Arab Emirates and the United States.

In terms of domestic business travel, some of this slack has been taken up by the rail network.

Both the National Express operated east coast line and Virgin Trains – which operates the main west coast line - say they have seen an increase in business-class passengers, though they refused to release exact figures.

A Virgin Trains spokesman said: "We are seeing a growth in business class passengers, whether this is for environmental or economic reasons."

Growing numbers of businesses are also using web conferencing solutions to replace many business trips. According to a recent survey by Wainhouse Research, the European web conferencing market grew by 49 per cent in 2007, with the UK achieving 29 per cent growth.

The research also claimed the UK market for web conferencing is set to continue to grow from $70.4m (£38.4m) to $154m (£84m) by 2012, a 17 per cent increase.