Cost Estimates for Building a Trail

from the Unified Corridors Investment Study (2019)

Capital costs Annual Maintenance
Trail alongside tracks $283 million $ 0.6 million
Trail only $221.5 million* $ 0.6 million

* This cost included an assumption that the RTC would spend $41 million in paying back  in state grant money and reversing the decision to implement passenger rail. However, the RTC Sept 3, 2021 agenda report indicates that railbanking would not require a payback:

Railbanking should not cause the RTC to payback any funding used to purchase the Santa Cruz Branch Rail Line. Funding was conditioned on initiating recreational passenger rail service and continuing freight rail service for as long as it is required by the Surface Transportation Board (STB). Recreational passenger rail service was initiated and continues at the Santa Cruz Boardwalk. STB’s approval of railbanking would temporarily suspend freight allowing the corridor to be preserved for other transportation uses, including potential future freight rail re-activation, consistent with the intended use of the corridor.