Brendan Simpkins

THE speed limit on the Gawler East Link Road is expected to stay at the current 50km/h limit following independent investigations.

An update was due to be provided for Gawler Council members at last month’s council meeting, but it was not reached before the 11pm meeting cap.

The investigations were undertaken following the passing of a motion on notice in November last that instructed council to act on increasing
the speed limit from the current 50km/h limit up to 60km/h for most of the road’s length, and investigate the possibility of increasing it to 80km/h.

Two engineering consultants were engaged by staff - Wallbridge Gilbert Aztec (WGA) and Tonkin Consulting.

WGA reviewed the increase of 50km/h to 60km/h, while Tonkin undertook the review into 80km/h.

Both assessments formed part of the report that was due to be presented to council, with both identifying a number of risks in increasing the speed limit.

The link road’s design is based on a design operating speed of 60km/h and signposted at 50km/h, with the 10km/h difference a road safety design principle that must be provided in order to meet current standards.

WGA’s review was based on a design operating speed of 70km/h for a 60km/h signposted limit, while Tonkin’s was based on an operating speed of 90km/h for a signposted limit of 80km/h.

Both found that increasing the speed limit would result in non-compliances in the road’s design, with horizontal and vertical curves of the road not compliant to current standards.

This would require significant modifications to meet design standards if the speed limit were to be increased.

Tonkin’s senior transport planner Paul Simmons said in his report that a “near complete redesign” would be required to increase the speed limit to 80km/h.

“It is expected that a design speed of 90km/h on the (link road) could not be feasibly delivered without a near complete redesign and reconstruction of a significant proportion of the recently completed roadway,” he said.

“This is likely to also include relocation of some of the utility services that were provided with the current roadway design.

“Furthermore, with the changes in alignment and cross section, there is expected to be significant change in the future residential development
of the vacant land on either side of the roadway. This would be exacerbated by restricting direct access to (the road) that would require
modification to the overall structure plan of the area.”

Changes to the road would include changes to sight distances at intersections; horizontal alignment; areas of cut and fill to change he vertical geometry of the road and changes to the cross section; and loss of roadside amenity.

The Department of Infrastructure and Transport carried out a traffic survey last October that noted motorists were either travelling at the 50km/h limit, or between 50km/h and 60km/h.

Fewer than 3000 vehicles a day utilise the road, well below the 12,000 that it can support a day.

The number of vehicles using the road is expected to increase once residential development in the surrounding area is complete.

It was recommended to elected members that council did not pursue any changes to the speed limit because of the significant costs it would
incur to bring it up to a complying design standard.

The report will go back before council for a decision at this month’s council meeting.