Abstract: A simple, compact and inexpensive chassis dynamometer capable of performing a multiplicity of tests and of simulating a variety of conditions, including wind resistance, weight of the vehicle and grade or slope of a road, includes first and second pairs of rolls for supporting the tires of a vehicle to be tested. An electric drive motor is connected with the rolls to drive them, and a single flywheel and associated eddy current motor are connected with the rolls to impart various levels of apparent inertia to the rotational movement of the rolls for thereby simulating the various conditions encountered by a vehicle travelling on a road. The frame is of open construction and the drive motor, eddy current motor, flywheel, rolls and associated components are confined within the periphery of the frame. The open construction of the frame simplifies the apparatus and enables maintenance and repair to be performed in situ.