except on special occasions such as New Year's Eve. Service operated every 5–10 minutes during the peak period, every 10–15 minutes during middays and during the day on weekends, and every 20 minutes during the evening until the close of service. Exact times varied from route to route. In March 2020, the system started to adjust train frequencies in order to accommodate for restrictions that were enacted in the wake of the COVID-19 pandemic. Trains would continue to run between 5:00 am and midnight daily, with late night weekend service being removed in order to accommodate for train cleaning. Fares and fare collection The standard Metro base fare applies for all trips. Fare collection is based on a partial proof-of-payment system. At least two fare machines are at each station. Fare inspectors, local police and deputy sheriffs police the system and cite individuals without proof of payment. Passengers are required to purchase a TAP card to enter stations equipped with fare gates. Passengers using a TAP card can transfer between Metro routes for free within 2 hours from the first tap. The following table shows Metro fares, effective December 17, 2021 (in US dollars): Transit Access Pass (TAP) and fare gates Metro has implemented a system of electronic fare collection using a stored value smartcard called the Transit Access Pass (TAP Card). This card was intended to simplify fare collection and reduce costs. In 2012, paper monthly passes were phased out and replaced with the TAP Card. As of September 2013, first-time Metro riders must deposit an additional $2 (or $1 at TAP vending machines) on top of their first fare payment to obtain a reloadable TAP Card. In addition, in 2008 Metro began installing fare gates at all underground stations, all elevated stations and some surface stations. Implementation of both programs (the TAP Card and the fare gate program) has turned out to be expensive ($154 million in total, so far) and its initial rollout was problematic. Ridership In , the Metro Rail system had a ridership of . As of , the combined Metro B and D lines averaged a weekday ridership of , making it the ninth busiest rapid transit system in the United States. Taking overall track length into consideration, Metro Rail's subway lines transport 7,960 passengers per route mile, making this the fifth busiest U.S. rapid transit system on a per mile basis. Metro's light