The busiest section of the Gauteng open-road tolling (GORT) system is between the Buccleuch and Allandale interchanges, in Midrand.
The traffic volume in both directions in 2016 reached 245 500 vehicles a day during the week, on average, says South African National Roads Agency Limited (Sanral) communications GM Vusi Mona.
During the morning and afternoon peaks volumes on the freeway reached between 10 000 and 11 000 vehicles an hour in each direction, he adds.
This is an almost 100% increase from 2006, when the average peak volumes between the Buccleuch and Allandale interchanges were between 5 000 and 6 400 vehicles an hour in the off-peak and peak directions, respectively.
Mona says the upgrading and expansion of the Gauteng freeway network, post 2006, has allowed for normal traffic growth, accommodating the roughly 4.7% increase in yearly traffic seen since 2010.
However, today the GORT system is close to capacity, he notes.
Around 133 000 vehicles an hour enter and leave the GORT network each hour during peak periods.
The morning peak period is between 06:00 and 09:00 and the afternoon between 15:00 and 18:00. However, Sanral has noticed that there is not much of a reduction in traffic volumes between the morning and afternoon peaks.
The growth in traffic demand results in the peak periods being extended by around 15 minutes a year, notes Mona.
“During the peak periods, many of the freeway sections carrying the peak direction demands are running at capacity – actually over the design capacity.
“There is only spare capacity on the off-peak directions and some limited spare capacity on sections of the N12 south of Johannesburg, as well as sections of the R21 during the peaks.
“There is some spare capacity during the off-peaks, but this is reducing as traffic demand increases.
Mona says traffic demand in Gauteng is predicted to continue to increase to 2020, which will have a detrimental effect on travel times. (Statistics show that Gauteng faces large-scale urbanisation pressure. Around 547 people arrive in the province every day.)
“Essentially the average travel time could increase by ten minutes between now and 2020, but will increase exponentially from then onwards.”