I have not seen nor came accross an arrestor bed in Kenya. It is more effective than speed humps. Speed humps will accelerate your death by tipping the vehicle over . In otherwords, arrestor beds are mostly found where the risk of runaway heavy vehicles is high i.e. in steep terrain, prior to tight bends and on approaches to toll plazas.
We should have an exchage program where Kenyan road designers are taken abroad to see first hand how to deal with the black spots. Salgaa, Londiani and many other dangerous roads reminds me of kisumu's Mamboleo/Kakamega/miwani interchange that has killed D.O. Misiani the musician amongst thousands of other Kenyans. It is nicknamed Kisumu's salgaa.
In SA there is a dedicated lane when a driver is in distress/mayday at such dangerous points. At the end of it....you are stopped by a mt kilimanjaro of river sand. Simple innovation but effective. In the US they use several drums filled with water.