http://www.engineeringnews.co.za
  SEARCH
Login
R/€ = 14.01Change: -0.01
R/$ = 10.63Change: -0.02
Au 1285.78 $/ozChange: -4.14
Pt 1423.00 $/ozChange: -1.50
 
 
Note: Search is limited to the most recent 250 articles. Set date range to access earlier articles.
Where? With... When?








Start
 
End
 
 
And must exclude these words...
Close Main Search
Close Main Login
My Profile News Alerts Newsletters Logout Close Main Profile
 
Agriculture   Automotive   Chemicals   Competition Policy   Construction   Defence   Economy   Electricity   Energy   Environment   ICT   Metals   Mining   Science and Technology   Services   Trade   Transport & Logistics   Water  
What's On Press Office Tenders Suppliers Directory Research Jobs Announcements Contact Us
 
 
 
RSS Feed
Article   Comments   Other News   Research   Magazine  
 
 
Aug 10, 2012

Variable speed limits not always effective, study shows

Back
Engineering|Road|Roads|Safety|Stellenbosch University|Transport|Western Cape|Christo Bester|Electronic Stability Control
Engineering|Road|Roads|Safety||Transport|||
engineering|road|roads|safety|stellenbosch-university-facility|transport-industry-term|western-cape|christo-bester|electronic-stability-control
© Reuse this



There is no reliable evidence of the safety benefits of buses and heavy trucks adhering to lower speed limits than passenger cars, suggests new research by Stellenbosch University (SU).

In 1999, following a fatal bus collision involving British tourists, the then Minister of Transport reduced the maximum speed limit for public transport vehicles (buses and minibus taxis) to 100 km/h. Heavy vehicles were already limited to 80 km/h.

SU civil engineering professor Christo Bester says there are a number of safety-related reasons why different speed limits could be applied to different types of vehicle.

For example, because of the differences in mass, different vehicles have different stopping distances. And, related to the inter- action between the tyres and the road surface is the ability of a vehicle to negotiate a horizontal curve. Excessive speeds can lead to a vehicle slipping, or overturning on a sharp curve.

Different vehicles also have different safety features, such as crumple zones, passenger restraints and electronic stability control.

However, despite these benefits, the application of variable speed limits is not without problems, with the most important of these being the ability to effectively enforce different limits on the same road, says Bester.

Variable speed limits are only regarded as effective when 85% of drivers keep to the designated limit. However, from studies carried out in the Eastern and Western Cape, 60% of minibus taxis did not comply with the speed limit, with the same being true for 64% of heavy goods vehicles.

Bester says automatic speed cameras cannot differentiate between vehicle types, which is why only the highest limit can be enforced.

Speed cameras that are manually operated or sophisticated apparatus with access to the South African vehicle database (such as the speed-over-distance camera) is necessary.

“It is clear, however,” emphasises Bester, “that minibus taxis and heavy vehicles do not adhere to their maximum speed limits. It is clear that these [variable speed] limits should be reconsidered or at least enforced on a larger scale than is currently the case. If the limits are not enforced, there is clearly no justification for having them.”

Bester also questions why legislation regarding the 80 km/h speed limit refers to heavy goods vehicles only.

“Why allow a higher speed limit for buses than for other heavy vehicles? Or vice versa – why force drivers of heavy goods vehicles to travel slower than heavy passenger vehicles?

“Some reason that the value of time is higher for passengers than it is for freight and, therefore, buses should be allowed higher speeds, but this is an economic decision and not one that relates to safety – the main reason given for speed limits. Economic decisions regarding vehicle travel should be taken by operators and not legislators.”

Another problem is that international research has shown that increased differ- ences in speed also result in higher crash rates, as faster and slower drivers have to be accommodated in the same road space. Particularly in two-lane, two-way roads, differentiated speed limits can result in reckless driving behaviour.

Bester says research has shown that the chance of being involved in a road acci- dent is lowest when the vehicle is travelling around the average speed of the surrounding traffic.

In the end, argues Bester, there is no reliable evidence of the safety benefits of variable speed limits. However, there is a concern that by increasing the speed variance, differential speed limits may increase overall accident rates.

“This is a solid argument against a differentiated speed limit between heavy vehicles and other road vehicles, and in favour of a standard speed limit for all vehicles.”

Bester then also suggests the introduction of a lower maximum speed limit for all vehicles, as proposed by the former Minister of Transport, as well as the further reduction of maximum speed limits on single lane roads, in line with international practice.

Edited by: Martin Zhuwakinyu
© Reuse this Comment Guidelines (150 word limit)
 
 
 
 
 
 
 
 
Other Automotive News
 
Latest News
Updated 5 minutes ago Vuli Cuba has resigned as chairperson of JSE-listed construction group Stefanutti Stocks. Cuba took up the position following the resignation as chairperson of Stefanutti founder Gino Stefanutti on July 15.
Updated 22 minutes ago South Africa’s development is being hampered by a serious shortage of skilled engineers, especially in the public sector, and the situation has been described as one of the worst capacity crises in years, a research report by professional body Royal Institution of...
Updated 1 hour 4 minutes ago To bolster its argument that renewable energy is critical to combating climate change, the World Wide Fund for Nature-South Africa (WWF-SA) has commissioned a series of reports that investigates the state of renewable energy in the country, focusing on how it can be...
More
 
 
Recent Research Reports
Road and Rail 2014: A review of South Africa's road and rail infrastructure (PDF report)
Creamer Media’s Road and Rail 2014 report examines South Africa’s road and rail transport system, with particular focus on the size and state of the country’s road and rail network, the funding and maintenance of these respective networks, and the push to move...
Real Economy Year Book 2014 (PDF Report)
This edition drills down into the performance and outlook for a variety of sectors, including automotive, construction, electricity, transport, steel, water, coal, gold, iron-ore and platinum.
Real Economy Insight: Automotive 2014 (PDF Report)
This four-page brief covers key developments in the automotive industry over the past 12 months, including an overview of South Africa’s automotive market, trade figures, production and the policies influencing the sector.
Real Economy Insight: Construction 2014 (PDF Report)
This five-page brief covers key developments in the construction industry over the past 12 months. It provides an overview of the sector and includes details of employment in the sector, infrastructure and municipal spending, as well as insight into companies’...
Real Economy Insight: Electricity 2014 (PDF Report)
This five-page brief covers key developments in the electricity industry over the past 12 months, including details of State-owned power utility Eskom’s generation activities, funding and tariffs, independent power producers and prospects for the sector.
Real Economy Insight: Road and Rail 2014 (PDF Report)
This six-page brief covers key developments in the road and rail industries over the past 12 months, including details of South Africa’s road and rail network and prospects for both sectors.
 
 
 
 
 
This Week's Magazine
South African State-owned defence industrial group Denel has announced its fourth consecutive year of profits. The group's results for the financial year 2013/2014 were recently announced at its head office in Centurion, south of Pretoria. Revenues grew by 17%, net...
There is little opportunity for JSE-listed infrastructure company Group Five to grow shareholder value in the domestic market, says CEO Mike Upton. He says value can still be found in the private sector, in the renewable and industrial power sector, as well as in...
The National Association of Automobile Manufacturers of South Africa (Naamsa) has announced the event dates of the 2015 Johannesburg International Motor Show (JIMS). The event will take place from October 14 to October 25, 2015, at the Johannesburg Expo Centre, Nasrec.
UK engineering support services provider Babcock is set to deliver the largest order of global truck manufacturer DAF’s truck tractors in Southern Africa to bulk carrier road-based logistics company Ngululu Bulk Carriers (NBC), with 133 trucks to be delivered in...
Digital radio communications in the African local government space can open up the world, but have many challenges to overcome, notes integration and migration of legacy radio communications infrastructure with digital mobile radio company Emcom Wireless head of...
 
 
Article contains comments
Updated 5 hours ago Business does not support the view that it should absorb the cost of e-tolling, Business Unity South Africa (Busa) said on Friday. "Business has always indicated its willingness to come on board and to explore the funding mechanism [for the improvement of Gauteng's...
Applications to keep certain court documents on the N1/N2 Winelands Toll Highway project secret were dismissed by the Western Cape High Court on Thursday. However, Judge Ashley Binns-Ward made orders that would effectively keep certain information under wraps until...
Article contains comments
The fuel levy is not an effective means of funding improvements to Gauteng's freeways, Consulting Engineers South Africa (Cesa) said on Thursday. "The fuel levy just spreads the burden among the entire population... roads have not really benefited from the fuel...
Article contains comments
Article contains comments
More
 
 
 
 
 
 
 
 
Alert Close
Embed Code Close
content
Research Reports Close
Research Reports are a product of the
Research Channel Africa. Reports can be bought individually or you can gain full access to all reports as part of a Research Channel Africa subscription.
Find Out More Buy Report
 
 
Close
Engineering News
Completely Re-Engineered
Experience it now. Click here
*website to launch in a few weeks