Quote by Norm Marshall (Smart Mobility, Inc.): “For the AM peak 2 hours northbound on the I-35 mainline across the Colorado River, the model is showing a volume/capacity ratio of 2.35 in 2010 where 1.0 is the maximum possible! I think this is resulting from a combination of a misspecified capacity value (I talked this over with the modelers when I was in town last time) plus an over-assignment of traffic by the model. The 2-hour traffic modeled there is 30,561 vehicles. As there are 4 northbound mainline traffic lines, this implies an average utilization of 3,833 vehicles per lane per hour. The theoretical maximum is 2,200 – 2,300 vehicles per lane per hour – BUT this requires traffic moving steadily. In stop-an-go conditions, the maximum flow is more like 1,800 vehicles per lane per hour. So the model is assigning roughly twice as much traffic as is actually there (or even could be there). As this can’t be true about 2010, it isn’t really worth the trouble to even look at the 2035 model.”

Related resource: Smart Mobility’s “Memo on CAMPO Traffic Model” (3/25/13)