Long overdue. Just make the whole stretch from Nakuru town to Total dual carriage way. The traffic thins out as some head to Eldoret while others divert to Kericho-Kisumu. Seem cheap to do considering there are not alot of structures on that road.
Then slowly work on making Nakuru-Nairobi dual. Rironi - Nairobi is being worked on. Work on bits and parts. Naivasha - all the way to Nakuru - should be dual also.