More than a quarter of large fleet managers are unaware of the impact of CO2 emissions on National Insurance contributions according to new research by Lex Autolease and YouGov.

The survey revealed that 29% of fleets with more than 500 vehicles do not realise the effect emissions have on NIC. This figure falls to just 10% for respondents who manage a fleet of 21-40 cars.

NIC costs is one of the biggest potential savings for fleets reassessing car policies said Keith Ball, executive director of lift and escalator firm Otis. It introduced a new car policy in 2008, which aimed to improve car choice for staff and up its green credentials.

Otis reinvested its savings to allow employees to have broader vehicle choice. However, workers can opt out of an improved car and instead receive a monthly 'green' cash incentive.

Just under half of Otis' 308-strong fleet is now under the new policy - these cars have average CO2 emissions of 123g/km.

In total, average emissions are 140g/km, a 6% drop from before implementation.

Ball said fleets must look at total life ownership rather than just leasing and maintenance costs to ensure optimum savings.

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