The first congestion pricing systems in the US were pioneered in California in the 1990s.[14] A 10-mile stretch of variably priced lanes on State Route 91 in Orange County continues to maintain average speeds of 60–65 mph even when speed in free lanes is as low as 15–20 mph.[15] The success of the State Route 91 express lanes prompted many other states and municipalities to follow suit. Counterintuitively, building a new express lane or converting a general-purpose lane into a HOT lane decreases congestion in both tolled and non-tolled lanes — at least for a period of a few years. This was the case on SR 91, as well as in Minnesota, where MnPass HOT lanes increased user speeds by 25 mph, and non-user speeds by 3–4 mph.[16],[17] Drivers are demonstrating that they place an increasingly high premium on their time. In Atlanta, home to one of the most successful express lane programs, the average number of daily trips on the I-85 grew from 7,300 in 2011 to nearly 29,000 in 2016 — even as the maximum toll price shifted from $5.55 in 2011 to $13.95 in 2016.[18]

The most obvious candidate for variable lane pricing is Los Angeles, which consistently ranks as the most congested city in the world.[19] LA currently has HOT lanes in two locations: on I-10 from Alameda Street to the I-605 (14 miles), and on the I-110 from Exposition Blvd to 182nd street (11 miles). Together, these two toll lanes cost $210 million to construct, and they have been highly successful. Speeds in the I-10 express lane remain roughly 24 mph faster than normal lanes.[20] However LA’s most congested roads remain un-tolled. A traveler on the 10 mile eastbound stretch of the I-10 from Exit 3A to Exit 12 in Los Angeles experiences on average 66 hours of delay a year.[21] Drawing on data from LA’s two variably priced lanes, the table below models the potential revenue stream from an express lane along this route.

LA’s Metro ExpressLanes charge low prices that do not reflect the premium drivers are willing to pay to escape traffic, and allow any vehicles occupied by two or more people to use the lanes for free. In our model, we assume that a new express lane from Santa Monica to downtown LA would charge an average of $4.50 per user, would only exempt cars with 3 or more occupants from the toll, and would impose fines proportionate to the fine-to-fee ratios of the other two lanes. Assuming that 10% of drivers on the given stretch of I-10 would opt into the lane (an average of usage rates on the other two lanes), this new tolling operation would generate over $100M/year. While it is impossible to determine time-savings in this model, LA drivers would save days of time on this one route alone. It would pay for itself almost immediately, and become an enormous source of revenue for LA County going forward.

Two straightforward ways to deploy revenue are constructing new roads/lanes and building a network of transportation tunnels beneath LA. Milling and resurfacing roads costs $312,500 per lane mile and building new road costs between $1–2M per lane mile, which means that our proposed express lane alone could fund maintenance of 320 lane miles per year, or the construction of nearly 100 new lane miles of road per year.[22] Tunneling costs vary widely depending on rock conditions, tunnel diameter, and density of support struts. Assuming difficult conditions, 1 mile of tunnel, 12 feet in diameter, would cost $11.6M/mile.[23] The West LA express lane would fund 8.6 miles of tunnel construction per year. These are only two possibilities — in the future revenue from congestion pricing may be deployed to finance more exotic forms of transportation such as electric vertical-takeoff-and-landing (VTOL) and the hyperloop.