The University of Tennessee, Knoxville


Managing Speed

by Airton Kohls (Source: World Health Organization)

While reading the latest TRB news, I came across an article from the World Health Organization on managing speed. It has been a topic of interest to me since 1996, when I started as a traffic engineer in southern Brazil. With the arrival of connected and automated vehicle technology, it is going to be interesting to see the interaction of speed limit obeying vehicles with our typical human inclination to drive faster than allowed by law. Is it me or are more and more drivers disrespecting the speed limits nowadays and, more importantly, imperiling lives on our roadways? Let me share with you some excerpts from this article including simple actions taken around the world to manage speed. To read it in full go to ( Speed has a positive effect on mobility in terms of reducing transportation times, but it impacts negatively on road safety, affecting both the likelihood of a road traffic crash and the severity of its consequences. Speed also has adverse effects on levels of environmental and noise pollution, and the "liveability" of urban areas. Over the last decade, along with greater global attention to reducing speed as part of efforts to reduce road traffic deaths and injuries, there has been a growing movement - often instigated at local level - concerned with strategies to manage speed in communities, and the potential benefits in terms of safer and more liveable streets. Approximately 1.25 million people die every year on the world's roads as a result of road traffic crashes. They are the number one cause of death among young people aged 15–29 years. As well as the public health impact of road traffic injuries, the disproportionate impact of road traffic crashes on the younger age groups makes them an important development problem: road traffic crashes are estimated to cost countries approximately 3% of their GDP, with the economic losses in low- and middle-income countries equivalent to 5% of GDP.

What are the factors which influence speed?

In addition to the speed limit posted on a road, a driver's speed is influenced by a number of other factors such as the driver's age and sex: in most countries male drivers and young drivers are more likely to speed and are therefore over represented in speed-related crashes. Other factors that may influence speed are the driver's blood alcohol concentration, and those related to the road layout and surface quality, as well as the power and maximum speed of the vehicle (see Figure below).

Driver Speed Choice

Saving pedestrian lives in New York City

New York City's ambitious target of reducing annual road traffic fatalities by 50% by 2030 aims to save 1600 lives between 2007 and 2030. To achieve this the city has installed pedestrian countdown signals at 1500 intersections citywide; implemented 75 additional 20 mph school speed zones; developed a pilot program for neighborhoods of 20 mph zones; enforced speeding laws along major traffic corridors; and used mass media campaigns to engage and inform the public. Depending upon the specific intervention being assessed, these measures have been credited with reducing pedestrian collisions and total road traffic crashes by 25–51%.

Ensuring in-vehicle technologies

Accelerating the penetration of proven life-saving vehicle safety technologies into the global fleet helps to reduce the number of people killed and seriously injured on the world's roads. This can be achieved through regulatory action by government or by voluntary commitment from manufacturers to make these technologies a standard feature of all vehicles. In the United States, twenty vehicle manufacturers representing 99% of the country's auto market have committed to make autonomous emergency braking (AEB) a standard feature in all new cars by no later than 2022. Their action was initiated ahead of any regulatory change by the Government. In addition to governments and manufacturers, consumers can also play a part by purchasing a vehicle fitted with these technologies.

Community support drives action on speed management

"Driving a mile through our streets at 20 mph instead of 30 mph adds just 60 seconds" was suggested by Myra James who was an environmental and sustainable transportation campaigner in Hebden Bridge, a market town in the Calderdale area of the North of England. In 2013 she formed a local "20's Plenty for Calderdale" campaign to specifically ask for a community–wide 20 mph limit on roads. After a successful meeting with the politician responsible for transportation, it was recognized that showing community support would be an important part of any speed limit change policy. She widened the campaign and activated other community groups by promoting the benefits for walkers and cyclists and the young and elderly as well as for the environment in terms of reductions in emission and noise that come with lower speeds. It became clear to politicians and Calderdale Council officials that there was strong community support for 20 mph limits. In May 2014 the decision was made by the Council to adopt a 20 mph limit for most urban and village roads across Calderdale and started a phased change of the legal speed limit for most roads from 30 mph to 20 mph through Traffic Regulation Orders. At the 2017 national "20's Plenty for Us" conference, Calderdale Council's Director of Public Health presented the results of the campaign: a reduction in casualties of 22% since the introduction of the new speed limits and sustained support from the community for the scheme with surveys showing 80% approval. Throughout the campaign, Myra had support and advice from the national "20's Plenty for Us" nongovernmental organization and in 2015 Myra was given their Campaigner of the Year award. Calderdale is just one of the many places adopting 20 mph speed limits for residential and urban streets in the United Kingdom.

Heart 20 mph limits


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