I see them occasionally on the roads. I think it is difficult to catch them, no license plates, no way of identifying them. If kena a road block, they will just scatter and easily evade the authorities.
Only way is to empower motorists to run them over. Use the video as evidence of the good deed, LTA pays for any repairs needed, and the motorist is rewarded with a complimentary car (a sportscar or luxury car) to drive in the interim. Plus a PBM title and more CDC vouchers.