Other Assumptions and Limitations

Traffic loads in CalME are applied by simplifying the tire contact areas into circular shape. The distance between tires in dual hubs is 1 ft (300 mm) on center. 

Currently CalME suggests a load spectrum for a given project location. The suggestion is meant for the truck lanes. For designing non-truck lanes, such as Lane #1 of a four lane (one direction) highway, the designer may need to choose a load spectrum that is lighter than the one suggested by CalME.

According to Truck Traffic Analysis using Weigh-In-Motion (WIM) Data in California, truck speeds typically fall within the range of 50 to 75 mph (80 to 120 km/h). Vehicle speeds are assume to be constant in CalME with a default value of 44 mph (70 km/h), which typically leads to slightly shorter predicted life than a speed of 50 mph (80 km/h).