There are special rules for estimating the value of the benefit of cars provided by companies for the private use of employees. If one's annual business mileage is 15,000 miles or less, the benefit of one's car is calculated at 30% of the original market value. That figure is reduced in cases of higher annual business mileage. If the annual business mileage is over 30,000 miles, the cash benefit is calculated at 6% of the original market value of the car. The tapering of rates is designed to ensure that employees who need to travel significantly in the course of their work incur a lower benefit in kind charge based on their yearly mileage. There is no evidence to suggest that it encourages employees to increase artificially their business mileage to maximise their tax position. Employees are unlikely to countenance such an approach because it would result in additional costs for employers, for example, by means of extra fuel costs. I consider that the current scheme's effect on the environment is relatively neutral.