One simple, effective, method is a travel decision tree. This is a series of questions for staff to consider before making a journey in their own car.

The first question is whether the journey is necessary or whether a telephone or video conference could be held instead.

If it is necessary, is it possible to use public transport, walk or cycle? If that isn’t an option, is a pool car or daily rental vehicle available?

Employees should also consider car sharing. Using a private car should be seen as the last resort.

Indeed, any employee reclaiming more than 5,000 business miles a year should be considered for the company car scheme.

“You should encourage people to use audio or video conferencing where appropriate,” says Watts.

“The key word is ‘appropriate’ because it won’t always be appropriate.”

Andy Mouland, project officer for transport at West Sussex County Council, suggests providing journey planning websites, ‘how to get to…’ leaflets and public transport maps and timetables.

Depending on the location of the organisation and staff, a well-managed pool car scheme or car club – whether it is run internally or by a rental company – is a realistic alternative to people using their own car.

A mileage cap on individual claims should be considered. Some organisations stipulate that for a single journey of more than 100 miles, a rental car must be used.

The number of miles at which to set the cap will vary by organisation, depending on their break-even point.

Another part of the ‘wider change programme’ is encouraging grey fleet drivers into lower-emission cars. This could be done through car parking incentives, for example, allocating car park spaces closest to the office to those with the lowest CO2 cars.

But what about getting senior management buy-in?

“Make them accountable for mileage costs,” Watts says. “Mileage costs are often a cost that goes through the business, without anyone paying attention to it, but if managers are accountable for the cost and responsible for bringing it down it will change their views.”

This is when grey fleet mileage data is key and it may be necessary to invest in a mileage capture system if the company expense system is not sufficient.

“The people that have been successful have decent data,” says Watts. “They understand the amount of miles being done by employees and know how much the grey fleet is costing.”