Heavy rain has disrupted transport on the busy Maai Mahiu-Narok road.
Motorists faced long delays on Thursday morning as parts of the road were blocked with debris and soil.
Narok East police commander Jared Marando told the Nation, that the road became impassible from around 2:30am near Suswa Girls Secondary School.
Two trucks, moving in different directions, he explained, stopped near the scene, causing a five-hour gridlock on the busy road.
"The two drivers feared driving past the blocked section as the soil was still heaped on the road," said Mr Marando.
Several motorists were forced to spend the night on the road, the police boss said.
The road was cleared early Thursday morning, allowing smooth flow of traffic.
The flash floods had also temporarily cut off the road between Duka Moja and Suswa but vehicles managed to drive through.
The road has in the past been impassible due to heavy rain.
In 2018, a section of the road developed a volcanic fault line and caved in.
Engineers from the China Communications Construction Company repaired the road.
Former President Mwai Kibaki inaugurated the Maai Mahiu-Narok Road on in 2011.
The road is usually busy as it connects Nairobi to the South Rift, Maasai Mara Game Reserve, western Kenya and Nyanza.
It is also an alternative route to the neighbouring Tanzania through Isibania in Migori County.