The 77 kilometre road will be upgraded from gravel to bitumen standard.
The Chinese are using the hanging basket technique to tackle challenges.
Work was expected to begin by end of this month and tenders had already been floated.
The project is aimed at curtailing the number of accidents along the dangerous spot.
Rising costs of roads rehabilitation is becoming a huge burden to the government.
The firm was picked from a group of eight companies that were in January invited to bid for the work.
Sinohydro Tianjin Engineering Limited will install the footbridges at a cost of Sh880 million.
Chinese engineers are racing to complete the the project by June next year.
The project will be completed in two years at a cost of Sh2.3 billion.
The Chinese-built railway began commercial operations on January 1.