Expansion of Toll Lanes or More Free Lanes? A Case Study of SR91 in Southern California

Abstract

This chapter applies the Southern California Planning Model (SCPM) to an important prototype application, a 10-mile segment of California SR91. SCPM is an integrated model that estimates trip production densities (and employment and population) for over 3,000 spatial zones in the Greater Los Angeles area at the level of 47 economic sectors. The possible widening of this route via extra tolled or extra general-purpose lanes has been the subject of considerable controversy. A non-compete provision in the franchise awarded to the California Private Transportation Company (CPTC) had stood in the way of public agenciesâ effort to provide additional capacity in the corridor. The approach sheds light on this controversy. The main finding is that, whereas congestion tolls are widely presumed to be efficient, the efficiency outcomes are complex when only a small part of the network is tolled. In sensitivity tests, the most plausible results, and the larges user benefits form adding a new tolled lane, are for the mid-range values of various assumptions. The result is consistent with recent theoretical investigations of second-best pricing. Flows on congested, untolled, parallel routes benefit from the addition of untolled facilities and this discussion is extended to an examination of the impacts throughout the Los Angeles network, including changes in destination choice by drivers and freight operators.