For example, the 680 lanes operate M-F, 5am-8pm. But northbound traffic in the morning isn't that bad, nor is southbound traffic in the evening. Almost no one would pay to use the express lane at these times, so you wind up with a lane that's almost completely empty and makes traffic denser in the other lanes.
Examples: 880 south between Hegenberger and San Leandro was 4 lanes, widened to 5 lanes in 2015 with the addition of an HOV lane, which was then converted to an Express lane. 880 interchange with 237 used to have the left hand flyover HOV only, which was converted to Express, so now everyone can use it.
