A recent state regulatory filing by SFMTA minces no words about where the blame lies for San Francisco's major traffic problems.

The filing, which SFMTA submitted before the California Public Utilities Commission, calls out Uber, Lyft and other transportation network companies (TNCs) for clogging the city's roads and polluting the Bay Area's skies.

"In 2016, San Francisco was rated as having the third worst traffic congestion in the nation," SFMTA writes in the filing. "Much of the increase San Francisco has experienced in vehicular traffic can be attributed to the huge increase in the number of TNC vehicles operating on city streets."

According to the San Francisco Examiner, some 45,000 Uber and Lyft drivers are now working in the city. By comparison, a mere 1,800 taxi drivers cover the same turf. A national study of traffic estimated that San Franciscans spend an extra 37 minutes each day stuck in traffic, a number that has been steadily rising since 2008.

The filing also asks the CPUC to conduct a full environmental review of the effect of riding-hailing companies. Primarily, however, the filing deals with the ability of ride-sharing drivers to use rental vehicles to do their job. As such, SFMTA wants those drivers regulated like limo drivers.

"Now, if TNC drivers can simply rent or lease a vehicle solely for the purpose of providing for-hire transportation, any distinction that may have existed between TNCs and other charter-party carriers based on the fact that TNC drivers operate vehicles obtained for personal use rather than vehicles obtained solely or primarily for commercial purposes has been eliminated," SFMTA writes.

"As a result, the rationale for applying different rules to limousines than are applied to TNCs no longer exists."

The tension over seemingly lax rules for ride-sharing companies is nothing new. For some time, taxi drivers have complained that companies like Uber and Lyft operate under far weaker regulations. Unlike taxis, which are regulated on the city level, Uber and Lyft rules are set at the state level.

Flywheel Taxi, a San Francisco-based cab company, filed suit against the California Public Utilities Commission last year over its regulation of Uber and Lyft. Flywheel claimed that the CPUC did not hold Uber and Lyft to the same standards as traditional taxis.