Check out this list of the Top 25 light-duty, medium-duty, van, and SUV fleets by size. A brief survey of several fleets in the list reveals their composition and applications.

Medium-Duty Truck Fleets

San Francisco (PG&E) utilizes 3,542 medium-duty trucks in its 9,010-vehicle fleet. Primarily Ford and GM vehicles, the fleet also includes International, Freightliner, Sterling, and Peterbilt models.

The trucks are used for utility body applications, light-duty bucket trucks, field mechanics, gas service vehicles, and telecom vans.

Of the total fleet, 260 trucks are bi-fuel CNG, and eight are dedicated CNG models.

Light-Duty Truck Fleets

with a fleet of more than 21,700 vehicles, operates 14,733 light-duty trucks. The trucks are mainly Ford, GM, and Workhorse models, utilized primarily for delivery and service. Pepsi-Co is testing a hybrid truck for potential incorporation into its fleet.

Utilizing primarily Ford and GM truck models,

operates 8,602 light-duty trucks in its fleet of 18,096 vehicles. The use of these trucks ranges from management vehicles to liquid spray protection.

runs 5,058 light-duty trucks in its 5,705-vehicle fleet. Used for the company's pest-control business, the fleet utilizes Ford, GM, and Dodge vehicles.

Van Fleets

operates 6,724 vans in its 7,807-vehicle fleet. Service technicians and engineers use the all-GM van fleet in working on local telecommunications and high-speed Internet in 18 states. Embarq has begun purchasing E-85 capable vehicles or those with a fuel management system. The company also plans to pilot a few hybrids later this year.

With a fleet of 39,689 vehicles,

utilizes 22,160 vans to transport employees and equipment to residential customer job sites. The vans are Ford and GM, and the telecommunications company plans to purchase flex-fuel vans in 2009.

SUV Fleets

Of

's 4,219 fleet vehicles, 1,153 are Chrysler and Ford SUV models. The SUVs are utilized for technical positions such as cell tower testing and maintenance. The company operates a few Ford Escape Hybrids in select areas.

The

fleet of 3,759 vehicles includes 1,184 SUVs, used primarily for high-terrain areas or as managers' "step-up" vehicles. The SUVs include GM, Toyota, Mazda, Hyundai, Ford, Mercedes, BMW, and Lexus models. The fleet currently operates one alt-fuel SUV.