The agency announced that it would reopen the ramp located near Museum Hill on Monday, September 20.
The section has been closed for three months, from June 28, when it was shut off to help with the construction of the expressway.
KeNHA Director General David Muchilwa noted that the extension was meant to help provide an efficient and reliable network.
Muchilwa has apologized for the inconvenience since the closure was making a major traffic problem but advised motorists to use alternative routes.
“This is to pave the way for the ongoing construction of the Nairobi expressway along Waiyaki Way. Motorists are kindly advised to use alternative routes,” Muchilwa noted.
The alternative, which mostly apply to Waiyaki Way Motorists joining Thika Road, is to branch to Chiromo at the exit near Kempiniski and off to Westalnds Road before rejoining Forest Road.
Since the construction of the Westlands-James Gichuru expressway began, motorists have had to use alternative routes and this has been time-consuming.
Many commuters who use Mombasa Road have opted for railway transport as some were forced to spend the entire night on the road.
This nightmare is however almost coming to an end. On August 25, KeNHA reported that the elevated highway was 73.2 per cent complete.
With these projections, KeNHA has notified that the Westlands to James Gichuru section is to be opened on September 30.
The Haile Selassie to UoN roundabout is also projected to be opened on October 15. The entire project is scheduled to be complete by June 2021.