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42 All the available data show, however, that the average trip length is least for the intrastate movement, greater for the interstate movement, and greatest for the transstate movement. While, therefore, the three classes are based specifically upon the number of States involved in the traffic movements, they also represent approximately and on the average, three ranges of trip length, from short to long.

Data of this sort are presented in table 9 for the same regions that are represented in the data of table 8. These additional data show clearly that, for truck traffic at least, the percentage of the main-highway movement originating in or destined to cities, rises with the increasing range of movement. For the seven States and regions represented in the table, cities are involved as the origin or destination or both in 87.0 percent of the intrastate or short-range movement, 95.5 percent of the interstate or longer range movement, and 96.7 percent of the transstate traffic, or traffic of longest range.

Although data similar to these for motortrucks in table 9 are not available for passenger cars or for the total traffic, it is highly probable that relations similar to those indicated for trucks exist also in the passenger-car and total traffic. If this is true, and the Committee believes that it is, then the Nation’s long-range highway traffic, and especially the interregional traffic, is in very large part a traffic moving between cities, or at least a traffic that has either its origins or its destinations for the most part in cities.

Traffic mounts at city approaches.—A glance at the traffic map, figure 20, will show how the traffic volume bands of the main rural roads represented increase in width as they approach the location of cities, indicating a steady increase of traffic volume with increasing proximity to the cities. In all cases the traffic volumes represented on this map are those observed at points on the highways outside city limits. In no case do the traffic bands represent the volume of traffic on extensions of the routes within cities; and in many cases the greatest traffic represented is that observed at points some distance—often several miles—outside the city limits. Particularly at the larger cities, it has been found impossible to represent by a convenient scale on any two-dimensional map the volume of traffic observed at