Category Archives: Cycling

Safer urban car lane widths

Posted on by 0 comment

Readers need to be aware that this post does have a bias toward giving weaker road users a higher priority for road space. My reading of these design manuals is therefore to identify the widths providing greatest benefit for people aged 8 to 80.
First warning: For this post, lane width is about the distance between painted lines or changes in road surface texture. Kerbs/road bumps greater then 50mm in height limit the available options. See the photo at the end of this post.

New Zealand legislation states that a “lane for the use of vehicular traffic … is at least 2.5 m wide” Reprinted 1 October 2017 – Land Transport (Road User) Rule 2004 (SR 2004/427)

Here is an example (in Schiedam) of narrowed motor vehicle lanes with the cycle lane width being maintained through the intersection. As we can all see, this doesn’t mean excluding heavy traffic (note bus stop). What it does mean is that the safety* a cycle lane width gives can be continued through the intersection.

*“Cycle lanes … provide a modest 10% safety improvement for cyclists, but 30% for pedestrians” This is from the NZTA Pedestrian planning and design guide Table 6.3

Data collected from the Minneapolis-St. Paul and Oakland County – Detroit areas does not support the idea of wider lanes being safer for motorists.

“There is no indication that the use of 3.0- or 3.3-m (10- or 11-ft lanes), rather than 3.6-m (12-ft) lanes, for arterial midblock segments (& arterial intersection approaches) leads to increases in accident frequency.” P23 (P25)

Ref: Relationship of Lane Width to Safety for Urban and Suburban Arterials – 2007 by Ingrid B. Potts, Douglas W. Harwood, and Karen R. Richard

Measures from Tokyo & Toronto also do not support wider lanes being more efficient for motorists. Ref: Narrower Lanes, Safer Streets – Dewan Masud Karim – 2015

Impact on Traffic Capacity and Congestion:

“Contrary to common belief, the results clearly demonstrate that narrower travel lanes, particularly 3.0m lanes, carry the highest traffic volumes (18% higher compared to 3.5m lane) … there is no measurable decrease in urban street capacity when through lane widths are narrowed from 3.7m to 3.0m … Traffic delays on urban roads are principally determined by junctions, not by midblock free flow speeds” p12

Large Vehicles and Narrower Lanes:

“Low volume trucks (less than 5%) experience no operational problems for narrower lane widths … For buses, it suggests using 3.3m for mixed traffic conditions and 3.0m where buffered bicycles lanes exist” p13

Lane widths to avoid – From Handbook for cycle-friendly design by UK based Sustrans 

“Avoid widths between 3.1 and 3.9m” p17

“Bus lanes widths … 3.2m to 3.9m to be avoided” p19

In my opinion it is particularly important that when narrowing lanes that kerbs and speed bumps are kept as low as possible. People stop for a variety of reasons. Bumps can make the ride in a bus uncomfortable or an ambulance trip worse than it needs to be.

Photo Gottingen – Lange Geismar Str

Past Blog post on lanes

A good one way cycle lane width = 2m+

4 lane roads when to

Lane width and cars per hour per lane

Number of cars per lane

Grey St too be 75% safer

Posted on by 1 comment

Over the past 7 years no less than seven people have died travelling to/from/within the Hamilton CBD.
Grey St, Hamilton East has recorded ZERO fatalities.

Better than that, the people from the Hamilton East Community Trust teamed up with HCC, NZTA and WRC to be one of six case studies around Australia and New Zealand being assessed by a team of Austroads traffic safety experts.
The outcome of the team work-shop was that safety improvements were identified that could easily halve the risk of serious injury to people visiting and moving through central Grey St.

Key safety improvements included treatments that helped to manage vehicle speeds, such as raised platforms, gateway treatments, road narrowing, textured surfacing and additional measures.

In fact the Hamilton East team clearly are looking for transformational change – they have a tick for every box.

The ticking of every box is the right thing to do; this allows different treatments to act together to give the greatest overall benefit.
Here are concept drawings showing how different treatments could give a reduction in the risk of fatality or serious injury of up to 75% for many road users.

Lastly page 14 of the Technical Report tells us we can do better than 75% safer:
“Typically this requires speeds below 30 km/h to avoid death if a collision occurs, or even lower speeds (around 20 km/h) to avoid serious injury. For a speed choice of 30 km/h instead of 50 km/h, the estimated reduction in fatal crash risk is 95%”

But this would be a political decision as it was in Helsinki in the 1990s. “The optimal speed limit on an urban street is the lowest limit the political decision makers can accept”

Link to report – Safe System infrastructure on mixed use arterials