UMTA ranked Metro's bus tunnel project as first among transit projects favored to receive federal funding in 1985, despite its reliance on unproven dual-mode buses. Metro tested a prototype Renault PER 180 dual-mode trolleybus in 1983, describing it as problematic after finding it exceeded freeway axle load limits by and having to replace several parts after several mechanical failures. Congress later appropriated $20 million to the City of Seattle for the bus tunnel project in October 1984, allowing for right-of-way acquisition to begin, but the funds were withheld until restrictions on new transit projects were lifted by the United States Senate the following May.