I have mixed emotions about HOV lanes.
In cities the size of Houston, Atlanta, or L.A. I totally get it and they should install HOV lanes. However, there is an example of how HOV's are installed without good intentions. When widening a freeway, a lot of cities will install HOV's just to get the extra federal funding for the project (HOVs promote carpooling, which leads to less carbon emissions; therefore, the federal government promotes the installation of HOVs with incentives). I guarantee this is why Memphis installed HOV lanes in the 1990s when they widened I-40 on the east side. Memphis does not have the population or the traffic congestion for them to justify installing HOV lanes. As a matter of fact, a few years ago, I heard they stopped enforcing the HOV lane on I-40. Signs are still there as of early last month when I was last there, but they haven't enforced HOV rules in years.
But overall I do agree with HOV lanes, the city just has to have the population to justify them.