A DESCRIPTION of two tests for car control, with results showing the effect of such variables as roll rate, load distribution, and tire pressure, is presented in this paper. Car control is defined by the author as the security with which the driver can maneuver his car over the highway, where he wants to and as he wants to, with precision and care. The two tests discussed were designed to find out what actually happens when a car goes around a curve, what factors are variables, and to set up a test procedure whereby these variables can be measured objectively, their relative importance determined, and the laws of their variation found.
In the first of these tests, the skid-pad roadability test, the specific problem is to measure the aspect of the car in relation to the pavement plane and the relative motion of various parts of the car under conditions of constant speed and travel in a circular path.
To study control problems that come during states of transition, when the car is entering or leaving a curve or when it passes from one curve info a reverse curve, or encounters cross winds, varying pavement slopes, or rough road surface, the second test described, a dynamic transition test called the “checkerboard” test, was devised.