All unlicensed passengers would create more traffic by taking a taxi alone. I think the only ones not allowed in the carpool lane should be a taxi with one pass

All unlicensed passengers would create more traffic by taking a taxi alone. I think the only ones not allowed in the carpool lane should be a taxi with one passenger (of course, in addition to the lone drivers). However, you could extend the logic further by saying that a lone taxi driver looking for a better fare causing a second taxi to pick up the unlicensed driver causes more traffic than a taxi with one passenger. So I've neatly saved the current carpool lane rules.