One reason why only licensed taxis can use those lanes is to prevent regular people using them. If you just needed to sign up to be an Uber driver, and you cou

One reason why only licensed taxis can use those lanes is to prevent regular people using them. If you just needed to sign up to be an Uber driver, and you could use the HOV lane, everyone would do it. Even if you had to do that and pay a fee of $5000/year, there would be plenty of people who could justify that over the time saved in traffic (but probably not Uber drivers).