Passage III

A consumer safety laboratory conducted 3 studies of vehicle braking performance under various conditions.

Study 1

Each of 3 identical vehicles was equipped with a dif­ferent braking system (System X, System Y, or System Z). Each vehicle was subjected to 10 trials on a dry road and 10 trials on a wet road. In each trial, the following steps were performed:

1. The vehicle was accelerated to 30 m/sec.

2. The braking system was fully engaged, and the vehicle's stopping distance, S (the distance required for the vehi­cle to come to a stop), was measured.

3. The vehicle's braking deceleration, B (the average rate at which the vehicle's speed decreased while the braking system was engaged), was calculated using the equation

The results of each set of 10 trials were then averaged to obtain an average S (in m) and an average B (in m/sec²) for each braking system on each type of road. Table 1 shows the results.

Study 2

Three hundred kilograms of cargo was placed into each of the vehicles that were tested in Study 1, and the procedures of Study 1 were repeated. Table 2 shows the results.

Study 3

System X was installed in a compact car, a sedan, a minivan, and a truck. The procedures for determining aver­age S in Study 1 were then repeated for each vehicle, with­out cargo, on both the dry and wet roads (see Figure 1).