Traffic lights vs circles

Chris Bennett, Noordhoek

With all of today’s traffic congestion, I wonder why the “traffic engineers” are not using more circles?

Circles are self regulating; they are cheaper to build; power cuts don’t affect them; circles are maintenance free; and they regulate enormous traffic volumes with ease.

When at last the officials eventually do make a circle, they immediately combine it with a dreaded traffic light, which is really counter productive (like the Heerengracht arrangement in Cape Town).

Can one imagine the wear and tear on brake shoes, clutches and all the wasted petrol caused by queues?

On visiting my son in Scotland, I saw that they believe in circles. On leaving his home, about 40km from the airport, we never stopped once during the trip. His father-in-law, in Holland, has never ever replaced his brake shoes with similar circles in operation.

The timing of lights causes frustration because sometimes the little arrow is incorrectly set for about 15 seconds then the total set turns red again. No one moves all sides waiting for lights. The bottom of Ou Kaapse Weg is a good example of this. It’s been like that for months.

Please people, let’s have a revolution and go circles, to save fuel, time and wear and tear. What do you say?

With the recent roadworks in the Fish Hoek Valley, I initially thought they were going to make an emergency landing strip for Boeings, it’s so big, the widening of the roads, costing millions, only to be constrained by another red light down the track.

Could the authorities please explain? Perhaps there is a logical reason? I cannot reason it out. The four-way intersection would have been the ideal spot for a circle?

* Felicity Purchase, mayoral committee member for transport and Fish Hoek ward councillor, responds:

The effectiveness of circles depends on a level of self-discipline and understanding of the rules of the road. On multi-lane circles, there are often problems due to drivers turning from the incorrect lane and not adhering to the arrow markings that are displayed on the road surface on the approaches to the circle.

The City has, in consultation with the national Department of Transport, initiated a pilot project where the so-called Fish-hook arrow has been tested in an attempt to assist drivers with pre-selection of the correct lane prior to entering the circle.

On the other hand, a traffic signal typically requires less mental effort from the motorist – they merely need to comply with the colour or arrow on the signal face, and act once checking that it is safe to do so.

A signalised junction can cost up to a third less than the cost of a large circle or roundabout.

However, signals have ongoing operational costs and this is why the City generally does a cost-benefit exercise when considering various intersection control measures, which includes the operational costs.

This analysis objectively weighs up safety costs (based on actual crash history), delay costs (based on measured delays) and implementation and operational costs. Software is used to analyse the projected improvements in a reduced delay, in order to ultimately choose the correct option for the specific scenario. Availability of abutting land is also a consideration when working on an existing intersection, as there are often geometric constraints due to private land abutting the site in question, and large circles / roundabouts typically require a footprint which projects outside of the road reserve boundaries.

The City has implemented battery-powered backup systems at key intersections on higher order mobility routes that carry a lot of traffic. That said, the battery system cannot charge fully when load shedding happens frequently.

The batteries are also prone to theft. These challenges hamper our efforts in limiting the impact of electricity outages on traffic flow.

Although operational costs for circles are lower, collisions at circles often lead to ongoing sign maintenance. Studies have shown that circles / modern roundabouts are effective up to a certain maximum threshold traffic volume. Thereafter, signals would offer a better all-round level of service. An example of this is the V&A Waterfront where a large roundabout was recently removed and replaced with a traffic signal and the queue lengths seem to have reduced since.

Having a circle combined with a traffic light is the exception. Traffic signals are implemented when the circle’s threshold capacity has been exceeded.

There may be no need to stop at a circle at lower traffic volumes, but queues do form at some circles during the peak hour periods.

The City applies the solution best suited to the situation and circumstances. Numerous circles are currently being implemented, typically as part of new developments as it is easier to implement a system of similar control measures when working on a new site, as opposed to trying to retro-fit into an existing network.

Residents are reminded to report any road related issues and/or complaints by calling 0800 65 64 63. We then conduct an investigation. If we do not know about it, we cannot fix it.