Transportation officials in Pennsylvania have eliminated passing lanes on a number of roads as a means of "traffic calming." Because motorists stuck behind slow-moving vehicles such as large trucks are denied the opportunity to pass, they, in theory, are forced to drive slower. The state department of transportation recently eliminated passing zones on a large stretch of Route 100 in Lehigh County.

"We're making a conscious effort to close out passing zones that we believe are not warranted, in order to improve safety." PennDOT engineer Dennis Toomey told the Allentown Morning Call newspaper. "What I think happens is, often people who are obeying the speed limit are not going fast enough for somebody."