The move could allow construction of the $232.7 million extension to begin late this summer, though final approval for a $75 million federal grant is still required and the lawsuit must still be formally withdrawn.
The group, Friends of Riverside's Hills, told local media it had obtained concessions worth about $3 million, involving noise reduction, hiking trails, and biking facilities.
Last May a judge rejected the environmental impact report (EIR) for the proposed line, ruling that the Riverside County (Calif.) Transportation Commission failed to address such issues as train wheel noise and pedestrian safety.
The rail extension runs roughly southeast from Riverside, Calif., the county seat, to Perris. Riverside currently is served by three Metrolink lines, the namesake Riverside Line and the 91 Line, both terminating as Los Angeles Union Station, and the Inland Empire-Orange County Line, connecting Riverside with points in Orange and San Diego counties, terminating in Oceanside.
The Perris Valley Line is considered an extension of the 91 Line, according to the Riverside County Transportation Commission.