San Diego State University Road Vehicle Performance Analytic Problems

1. Part 1 – Analyze  Pick a vehicle of your choice (incl. yours). Using Microsoft Excel (or a similar program) plot this vehicle’s theoretical stopping distance (in feet) vs. speed (in mph) for speeds of 0 to 120 mph (Eq . 2.42). Assume there are two people in the vehicle. Assume the following parameters:

• •Braking efficiency = 95% for antilock brakes, 80% for non-antilock brakes
• •Coefficient of road adhesion = 0.70
• •Grade = 0% (flat)
• •Air density = 0.0024 slugs/ft3 [Note: 1 slug = 1 lb force/(1 ft/s2 acceleration) and 1 lb force = 1 slug*ft/s2 = 4.448N]
• •Mass factor = 1.04
• •Look up the following vehicle characteristics: coefficient of drag & frontal area (see next slides), weight (unloaded with two people in it)
• •Draw conclusions – INCLUDE A PDF of your work & conclusions

2. : On the same graph as Part 1, plot practical stopping distance (in feet) vs. speed (in mph) for speeds of 0 to 120 mph. Use the AASHTO braking distance formula (Eq . 2.47)