Nairobi Expressway:
what you are actually buying.

A toll road with a fixed number of doors

The Expressway runs above and alongside Mombasa Road, Uhuru Highway and the start of Waiyaki Way, from Mlolongo in the south east to James Gichuru in the west. You join and leave it only at its interchanges, which include Mlolongo, the SGR and JKIA turn-offs, the Eastern Bypass, the Capital Centre and Haile Selassie ends of town, Museum Hill, Westlands and James Gichuru.

That fixed set of entry and exit points is both the whole point and the whole limitation. It is a bypass of one corridor, the Mombasa Road to Waiyaki Way run through the middle of the city. It does nothing at all for Thika Road, Jogoo Road, Ngong Road, Langata Road or Outer Ring, and joining it for a short hop between two adjacent exits rarely buys you anything.

Tolls vary by vehicle class and by the pair of interchanges you use, and they change from time to time, so check the current rate for your own trip rather than relying on a figure someone quoted you last year.

When it is worth paying for

The honest answer is that the saving is largest at exactly the times the ground road is worst, and close to zero the rest of the time.

Worth it: a long run across most of its length during a peak. The airport to Westlands or Museum Hill between 6:30 and 9:00, or the reverse between 5:00 and 8:00, is usually the single biggest time saving available anywhere in Nairobi. Catching a flight is worth it almost regardless, because what you are really buying is predictability rather than speed.

Usually not worth it: off-peak, when Mombasa Road and Uhuru Highway are moving and the difference is a few minutes. Short hops between neighbouring exits. And any trip where your destination is not close to an interchange, because you will pay the toll and then spend the saved time on ordinary roads at the other end.

Where it still queues

An elevated toll road does not create capacity on the roads it lands on. That produces two kinds of delay that catch people out:

• The toll plazas: entries back up at peak, and the queue to get on can eat into the time you are paying to save. Know before you arrive whether you are using an electronic tag or a manual lane, because picking the wrong one and having to cross at the plaza is how short queues become long ones.
• The off-ramps: the more important one. The Expressway delivers a concentrated stream of vehicles onto an ordinary road at a single point. In the evening the Westlands and James Gichuru exits are the classic example: you pay to skip the city and then join the Waiyaki Way queue anyway, a couple of kilometres further along. Museum Hill behaves the same way when the CBD is busy.
• The airport interchange: busy around departure banks, and it shares its approaches with ordinary airport traffic.

The rule that follows is simple enough. Judge the Expressway by the road at your exit, not by the road under it. If your off-ramp leads somewhere that is also jammed, most of what you are paying for disappears at the ramp.

Things worth knowing before you use it

• It is a restricted road: no boda bodas, no pedestrians, no stopping. If you break down you are waiting for the operator's recovery, not flagging down help.
• There is no exit once you commit: miss your interchange and the next one may be several kilometres on, with a toll to match. Decide your exit before you join.
• Weather matters more up there: the elevated section is exposed, and heavy rain cuts visibility and makes the ramps slick. In a downpour the ground road is sometimes the calmer choice.
• An incident on it closes your options: a blockage on an elevated carriageway with no hard shoulder and no side roads takes far longer to clear than the same incident on Mombasa Road.

How Expressway closures get announced

The Expressway operator announces closures, incidents and maintenance on the road itself, and is the authority for anything on the elevated section. KeNHA handles the ground roads beneath and either side of it. NTSA and the traffic police cover incidents on both.

The distinction is worth holding onto, because the two roads get confused constantly. An incident on the Expressway does not mean Mombasa Road is blocked, and a jam on Mombasa Road does not mean the Expressway is affected. Quite often one is the answer to the other. Knowing which of the two has actually stopped is the difference between a good decision at the toll plaza and an expensive one.