A comparative study of the safety performance of asymmetric and standard HPR windshields was conducted. The effect of increased interlayer thickness was also quantified. There were four different types of asymmetric windshields which had inner layer thicknesses of 0.8 to 1.5 mm and interlayer thicknesses of 0.76 and 1.14 mm.

The experimental program consisted of both full scale sled tests and headform drop tests. A total of 127 vehicular impacts were carried out using a modified Volkswagen Rabbit. The test subject was a 50th percentile Fart 572 anthropomorphic test device. The asymmetric windshields were found to have a lower lacerative potential than that of the standard windshield. The best TLI value of 5.2 was provided by a 0.8 - 0.76 mm windshield at 60 km/h. That for the standard windshield was 7.7 at the same speed. All HIC values were less than 1,000 at 48 km/h.

The drop tests were designed to study head injury potential at velocities below 30 km/h at which the windshield may not fracture. The HIC value for standard windshields was found to be as high as 800 without fracture. Tempering of such windshields can increase the hazard. Non-fractured asymmetric windshields did not exhibit dangerous HIC values.