The Federal Road Safety Corps Marshall advised commercial bus owners to install speed limiting devices in their vehicles.
So i researched about what the device entails and came up with the following summary.
Its either called a speed governor or speed limit.
Here's how it works: A series of sensors detect how
fast you're going, then communicate that
information to the engine's computer, which
manages nearly all the engine's functions. Once you
reach a pre-determined top speed, the computer
steps in and restricts the flow of air and fuel to the
engine and even the sparks that cause combustion.
Either way, you'll be unable to exceed the top speed
as determined by the car's manufacturer.
But to know everything about it,click the link below
www.wikipedia.org/wiki/Governor_(device)

Very helpful information

One thing is to introduce this device into Nigerian cars and roads; another is to get the drivers to play by the rules and encourage them not to counterfeit the device product or patronize from quacks who may come out to say they are selling it. The technology of this speed limiting device is very sensitive but if it fails, the lives of passengers and driver may be seriously in danger.

Op, I thought you will explain this. It's same principle Steam and Gas turbine governors work.

DStvWorldMedia:
One thing is to introduce this device into Nigerian cars and roads; another is to get the drivers to play by the rules and encourage them not to counterfeit the device product or patronize from quacks who may come out to say they are selling it. The technology of this speed limiting device is very sensitive but if it fails, the lives of passengers and driver may be seriously in danger.

There is a safety device called OVER SPEED TRIP (OST) which protects the system when the shaft goes to over speed. OST shuts down the system In case of any governor malfunction.