If you’re planning to get your kicks on Route 66 this summer then make sure you put the environment at the top of your agenda.

Anyone planning a road trip across America, perhaps as part of a gap-year holiday, should think carefully about the car they choose to rent with most of America’s leading rental firms now offering a number of green cars in their fleets.

Enterprise-Rent-A-Car is leading the way with a whopping 4,000 hybrids in its fleet - mainly the Toyota Prius; while Alamo and National boast another 1,000 hybrids. Enterprise has 6,500 branches across the USA mainly concentrated in metropolitan areas, so finding a vehicle that’s right for you shouldn’t be too difficult. The company also offers a Keys to Green programme in which you pay an extra $1.25 per rental to purchase carbon offsets from TerraPass.

Hertz meanwhile has an extensive green collection, with 3,400 Prius vehicles in its ranks. There are also a number of fuel efficient non-hybrids in the fleet including the Toyota Camry, Hyundai Sonata and the Ford Fusion.

Avis too boasts a number of green options including the Toyota Prius, Nissan Altima and the Ford Escape.

Meanwhile, if you’re travelling to a particularly environmentally conscious corner of the USA, you can check out the electric cars on offer at several small rental agencies: for example Electric Time Car Rentals offers GEM electric cars in San Francisco; Fox Rent A Car has several hybrids in its West Coast locations; and in Maui, Bio Beetle offers cooking-oil powered Volkswagen Beetles.

Remember to book car hire in advance to ensure you get the vehicle you want. Â