 The Metropolitan Transit System (MTS) completed the 6-mile extension of the Trolley east through Mission Valley to La Mesa via an underground tunnel at San Diego State University (SDSU) in July 2005.
SANDAG’s Service Bureau was retained by MTS to examine ridership on the Green Line — conducting three surveys in late 2005. Data was obtained via onboard passenger surveys, online surveys of SDSU students, and passenger counts at the SDSU Transit Center.
Results of the survey [PDF] indicate that the Green Line has succeeded in attracting new transit passengers and addressing unmet transit needs in the region. It has generated about 18,500 daily trips, 7,200 of which are by new riders. The Green Line also is relieving congestion on the roadways – diverting 4,600 trips from automobile to transit, and reducing parking demand at SDSU by 2,000 cars per day. The busiest stations on the Green Line are Old Town and SDSU.
The Green Line is succeeding in achieving one of the main goals of regional transit — attracting new riders. Nearly 40 percent of Green Line riders did not use transit during the previous year. Passengers are also riding more frequently. Before the Green Line’s completion, about 53 percent used transit five to seven days per week. After its completion, this number jumped to almost 63 percent.
The SANDAG survey also yields interesting data about Green Line passengers themselves, including their preferred means of payment, reasons for using the service, and overall impressions of the new low-floor vehicles. For example, two-thirds of Green Line riders use passes (41% monthly pass; 26% college pass; 5% day pass), while 20 percent use cash.
Passengers’ reasons for using the trolley service vary. The main reasons given by those surveyed were: no car (39.2%); avoid traffic congestion (28.2%); cost of driving (25.4%); parking hassles (21.6%); environmental benefits (19.6%); faster than a bus (14.5%); more time to read and relax (13.3%); and easier than driving (11.3%). Most trips on the Green Line are between home and school or home and work.
Finally, 82 percent had a favorable overall impression of the new state-of-the-art trolleys — the Siemens S-70 light rail vehicles that efficiently move passengers up and down the Green Line. | 
