Category Archives: Politics

Speed Design Vs Posted Speed

Posted on by 0 comment

The point of this post is to show a weak link between design speed and posted speed, and to illustrate that the optimum posted speed limit is set more by leaders than engineers.

A 5 km/h speed sign is what one sees when entering the car-park at Te Rapa PlaceMakers, while entering Bunnings car-park the speed is assumed to be 50 km/h. They are similar car-park designs, types of business and client types.

A 10 km/h speed limit is used at all supermarket car-parks unless you’re shopping at Countdown

15 km/h is the speed at Countdown supermarkets, unless you shop at Countdown Liverpool St, which is 10km/h. There are no engineering, design, franchise or user differences. What makes things different is the managers’ thinking about the level of risk and what is a ‘reasonably practicable’ speed to reduce the risk of harm.

20km/h is a benchmark speed. The AustRoads safety team, which led the Grey St safety improvement plan, mentions that speeds of around 20 km/h are used to avoid serious injury. A 20km/h limit is used in the German city of Koblenz for its city centre streets. The road use in central Koblenz isn’t different to Hamilton’s Barton St (30km/h) or Victoria St (50km/h between Bryce St and London St); only the risk of serious harm from speed is different.

30km/h is now what 50km/h was last century. Most urban areas in Europe use 30km/h as a default speed. There is a good reason: “for a speed choice of 30 km/h instead of 50 km/h, the estimated reduction in fatal crash risk is 95%” (from the AustRoads safety team that led the Grey St safety improvement plan). Even the Chief Executive of AA advocates for 30km/h speed limits. In Seattle, the speed limit on all residential (non-arterial) streets is 20 mph [30km/h], and the speed limit on arterials is 25 mph [40km/h], unless otherwise posted. Speed is the critical factor in the severity and frequency of crashes. Learn more about why Seattle lowered speed limits in 2016.

A 40km/h [25 mph] default speed is used increasingly across cities in the USA. Speed is the key to reducing the severity of harm resulting from mistakes. For Example: “Since 2014, [in] New York City … the city’s traffic fatalities have declined 28 percent with a 45 percent decline in pedestrian fatalities — bucking national fatality trends, which have increased 15 percent over the same period.”

50km/h is a misused speed in urban areas. It is seen to be an efficient speed for journeys that involve moving a very large number of motor vehicles along a single lane. The problem is that cities are made up of places, where people walk from homes or car-parks to socialise face-to-face, to shop, to go to school, or many other day-to-day activities, all of which involve crossing roads as pedestrians. A pedestrian will be almost always seriously harmed, and in fact has a 50% chance of being killed in a conflict with a person driving a car travelling at 50km/h. Never mind who makes the mistake, the pedestrian is always the victim.

Zero Harm is safer than Safe Journeys

Zero Harm’s objective is that

“By 2020 or sooner all our people*, regardless of employer, will go home safe and healthy, every day, no exceptions”

“Our Safer Journeys ads sometimes employ a shock tactic; for Zero Harm we suggest a slightly different take, adding in an emotional campaign with faces of collegues who care, wives, husbands, partners and children who want you to come home to them safely.” NZTA Highways Information Portal Zero Harm Strategic Plan 2014-2020

Safe Journeys argues for “A safe road system increasingly free of death and serious injury” Statement from March 2010 – Safer Journeys Strategy to 2020.

“If we continue with our current approach, and rely on our existing set of road safety initiatives, it is estimated that in 2020 around 400 people will still lose their lives” (p. 9)

[Sadly only] “alert, skilled, unimpaired drivers should expect to reach their destination without mishap every time” (p.11)

And of serious concern is the fact in the seventh year of Safe Journeys, we still have a road system that is increasingly killing responsible people who sometimes make mistakes in their use of the roads.

Lastly, and most disappointingly, the Ministry of Transport’s official summary of submissions to Safe Journeys referred to Vision Zero as “radical” in response to submitters that urged a ‘Vision Zero Strategy’ (p.12).

As the graph above shows countries setting Ambitious Targets are forgiving more people that make mistakes.

Graph from Quarterly road toll report:  http://www.transport.govt.nz/research/roadtoll/

Category: News, Politics, Safety