Simple! Remove cash from the system and enforce salary.
Drivers generally drive fast, break road rules etc all because they want to carry as many passengers for the day as possible. They basically have a quota to pay taxi owner per route/taxi and usually pocket excess or part there of. Obviously this is where tax avoidance comes in as the entire system under reports income to pocket money that really should be going to gov & RAF.
Government needs to force a cashless system I these guys and make cash paid on transit illegal. Then, they won't do this but, need to ensure that 50% of taxi tax revenue goes directly to RAF as they are the cause of most accidents and also force minimum 3rd party insurance cover.
By making the taxi owners part of such a cashless system, it forces indirectly tax compliance and since drivers then become employees with salaries

unions come in too haha. Road rule compliance takes care of itself as there is now formal employment, so prdp becomes mandatory or else owner gets nailed (he draws cash from sales), and salary is tied, bonus can be made I guess as incentives but driver no longer can pocket infinite funds as present. You'd be surprised how much these okes make weekly considering they have zero degree/diploma/formal skills
All in all.. The point is simple, gov can only fix the system if they have the taxi owners by the balls, ie the cash/funds flow. Will they do it? No.. The gov knows too well that there would be havoc as a result hence they have been pushing city initiatives to indirectly push taxi system out