Many commuters in Kenya's capital, Nairobi, have had to walk to work as most minibuses have not been fitted in time with new digital speed monitors.
The regulations mean that every public transport vehicle must have one to ensure they do not go over the 80km/ph (49mph) speed limit.
Those minibuses that have had them installed have doubled their fares.
Officials say out of 60,000 registered minibuses, known as matatus, only 8,000 have so far fitted the monitors.
The monitors cost 45,000 Kenyan shillings ($520, £312) each and will allow the police to track speeding vehicles.
However, suppliers say the monitors are now out of stock as most taxi operators waited until the last minute to purchase them, the BBC's Caroline Karobia reports from Nairobi.
The government has refused to grant an extension to the 31 March deadline, saying it had given ample warning, she says.
The regulations were introduced in December in a bid to curb road accidents, our reporter says.
Matatus are the main mode of transport in Nairobi.
Last month, matutu operators in Nairobi went on a one-day strike over an increase in parking fees introduced to ease congestion in the city.