One-Way SBF’s: Why Option One? SAFETY!

This post is by Dr. Hank Weiss, an injury epidemiologist with over 3 decades experience in injury prevention research and practice, and a SPOKES member.

Properly designed uni-directional separated/protected bike lanes
are the safest on-road urban design
when they cross driveways and intersections

Recently, a New Zealand Transportation Agency (NZTA) and Dunedin City Council (DCC) staff working group released an ‘update report’ describing options for separated cycle lanes along the dangerous SH1 one-ways in the Central City. Just getting underway is a period of public comment as NZTA begins reviewing the preferred options. The report recommends two options for further consideration. Both options offer people who cycle greatly enhanced mid-block vehicle protection from being hit from behind and car door hazards. However, there are important differences that arise for each.

Option 1 – The first option features a uni-directional (one-way) 2.6m separated cycle lane Separated Bicycle Facility (SBF) on the right-hand side of each of the SH1 one-way streets, with cyclists riding in the same direction as the traffic (both mid-block and intersection example profiles shown below). This was the top option favoured by the working group.

Figure 1. Example uni-directional mid-block profile.

Figure 2. Example uni-directional intersection profile (barriers do not go through intersection).

2) The second option entails a 3.2m bi-directional (two-way) separated cycle lane SBF along Cumberland Street with cyclists riding in two-way formation along the right side (both mid-block and intersection example profiles shown below).

Figure 3. Example bi-directional mid-block profile.

Figure 4. Example Bi-directional intersection profile (barriers do not go through intersection).

Safety Rationale for Recommended Priorities
I wish to focus on the safety advantages of Option 1, the uni-directional separated cycle lane. To do so, I will revisit SPOKES’ earlier discussion of the findings from a Canadian study and a recent further analysis of these data. I also draw from a recent cycle tracks safety review paper (Thomas et. al, 2013).

SPOKES blog readers will recall that Teschke et. al (2012) found much greater safety on Canadian cycle tracks when compared to cycling on major streets with only painted bike lanes or no bike infrastructure at all. They found, for example, that cycle tracks were about six times safer than unprotected bike lanes with parked cars, and nine times safer than streets with parked cars and no lanes or infrastructure. Bike lanes with vehicle parking were about 7 times riskier than fully protected lanes.* In the second peer-reviewed paper from this study, more attention was paid to road section types and what settings and configurations were safer than others.

1. Intersections
When cyclists arrive at an intersection from the opposite direction to traffic in two-way situations (option 2), most studies show the crash and injury risk goes up substantially. In Harris’ et. al. analysis, the opposite direction scenario at intersections resulted in a large elevated risk ratio of 7.8 (95% CI = 2.0-30.3) compared to uni-directional tracks.

Astute observers will find online references to some older European studies (for example, [Jensen, 2008] suggesting that protected cycle tracks might be less safe than unprotected bike lanes. Such findings, however, were based on older studies that: a) combined either shared pedestrian paths and protected tracks or uni-directional and bi-directional protected tracks into single analytical categories, b) used absolute numbers instead of rates, c) did not take injury severity into account, or d) had statistically insignificant results. When uni-directional protected cycle tracks are analysed separately they stand-out as the best option for reducing serious injury (Thomas et. al, 2013). In summary, properly designed uni-directional separated/protected bike lanes are the safest on-road design when they cross driveways and intersections.

Intersection considerations and design treatments are important for all types of cycle infrastructure because about 60% of bike/motor vehicle crashes occur at intersections. A protected track in the same direction as the traffic doesn’t appear to add any more intersection risk than unprotected lanes (they essentially become unprotected lanes at intersections because turning cars must cross them). But adding new protected lanes creates the opportunity for improving safety even more by upgrading intersection designs to modern practice. Key concepts to improve cycle intersection crossings include the following (adapted from Cycle Toronto and Thomas et al.):

  • At intersections, bring the cycle track closer to parallel traffic for visibility.
  • Place a motor vehicle traffic stop line at least 20m before intersections.
  • Mark cycle crossings through the intersections (just as crosswalks mark pedestrian paths).
  • For unsignalised intersections, where the cycle track is running along the priority road, it can help to keep cycle track and footpaths elevated through the crossing (essentially a speed hump).
  • At signalised intersections, (1) traffic signals can be used to limit conflicts between cyclists and turning cars. Where those conflicts are not entirely eliminated, (2) use of geometric measures such as tight corner radii, medians and speed humps can help ensure that turning traffic moves slowly. With years of trial and error, many consider the Dutch Junction design state of the art.
  • Modern technology allows signals that can control the cycle track when the time that it is safe for bikes to cross differs from the time that the parallel traffic phase is green.
  • Reduce the number of motor vehicle turns across the cycle track by offering parking on the opposite side and limiting cross traffic turns by time, vehicle type or place.
  • Eliminate bus/cycle conflicts by opposite road side separation (as chosen for both Dunedin SH1 options).

Winner: Strongly in favour of Uni-directional option

2. Driveways
Conflicts between cyclists from vehicles turning into driveways will remain mostly unchanged with the uni-directional option unless the right side of the street has more or fewer driveways than the currently used left side. The removal of parked cars, however, has the extra benefit of improving motorist visibility of cyclists and pedestrians while turning into driveways. It is hypothesised that a bi-directional track could lead to some drivers overlooking the contra-flow cycle traffic during drive-way manoeuvres, but to our knowledge this has not been quantified. Removal of parked cars from alongside the cycle track will also reduce existing hazards by opening up sight-lines between vehicles pulling out of drive-ways and cyclists. Various means of signage and elevated entries can help further improve awareness during driveway manoeuvres.

Winner: In favour of Uni-directional option

3. Right-hand intersection or driveway turns
The right-hand lane placement on the one ways for both options may offer increased motorist visibility of cyclists during vehicle right-hand turns since the driver will now be on the same side of the vehicle as the cyclist, reducing vehicle blind spots. However, we are not aware of studies that have quantified this. On the other hand, with a larger turning radius, right-hand vehicle turns may obtain higher speeds which could negate visibility benefits. It is unknown how these factors might be different for cycle traffic moving in the same or opposite direction. Intersection studies suggest on first principles that it will be better for uni-directional cycle travel. We have talked to a road engineer in San Francisco where an opposite side uni-directional buffered track has been in place and they reported no particular turning issues.

Winner: Toss-up

4. Usable Road Width
A two-way cycle lane will take up more width along the road way right-of-way, while typically allocating less room per lane of cycle traffic. This has safety ramifications for all road users. In the mid-block profiles proposed above, for each lane of cycle traffic the bi-directional lane allocates 1.6m vs 2.6m for the uni-directional lane. Therefore, the uni-directional lane allows for passing without concern for oncoming cycle traffic, has more room for passing, and offers more comfortable and social riding. In addition, the greater overall width of the bi-directional option (3.2m vs 2.6m) means narrower lanes for motor-vehicles, since the extra width has to come from somewhere (if the road is not widened to accommodate it).

Winner: In favour of Uni-directional option

Artist impression of Uni-directional design on Dunedin's One-way system.

Artist impression of Uni-directional design on Dunedin’s One-way system.


Overall Safety Winner: Option 1 – Uni-directional separated lane

Editors Note: Section 4 was added November 29 and the last photo switched-out


Take Action NOW!

SPOKES urges its members, friends and all concerned citizens to consider the options outlined in the NZTA/DCC report and consultation website and support the need for some form of separated lanes. If you agree with the above safety analysis for the recommended uni-directional option, we encourage you to mention that as well. SPOKES has made it very easy to quickly do this on our own Submission Website.


*Other recent studies also show the relative safety of separated cycle tracks:

  • 3 cycle tracks in NYC showed a decrease in total cyclist injuries: 9th Ave: -57%; 8th Ave: -30%; Prospect Pk West: -62% (NYC Department of Transportation).
  • Sevilla, Spain: Construction of 164km of cycle tracks led to a halving in cyclist serious injury rate per 100,000 trips from 2006 to 2010 (personal communication via John Pucher from Ricardo Marqués, Universidad de Sevilla).
  • In a study of 19 cycle tracks in the USA, the average injury rate per million bike km was much lower on cycle tracks (2.3) than on roads without cycling facilities (range of 4-54 in other published studies). (Lusk et al., 2013, Am J of Public Health).
  • In Montreal, a study of 6 cycle tracks showed an average cyclist injury rate 28% lower than on nearby “reference streets.” (Lusk et al, Injury Prevention, 2011).
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3 Responses to One-Way SBF’s: Why Option One? SAFETY!

  1. patrickmorgancan says:

    Great info. Thanks Hank. Here in Wellington we are considering two options for Island Bay Parade: kerbside or street side protected cycle lanes.
    And a few would like to see a 2-direction cycle way.—shorland-park-to-wakefield-park

  2. dunedinbiker says:

    There’s lots of things that this article fails to address. The justification by the NZTA for placement on the RHS of the road is based on false premises (buses don’t have doors on the RHS to open into cyclists’ way, buses are relatively rare, bus stops could be recessed into the footpath (the footpath is wider than the cycle lane!), and there are just as many driveways/business entrances on both sides of the road). Also, the reaction to the cyclist deaths has largely been an emotional one and not based on the actual reasons why the “accidents” occurred. These were poor cycle facility design (NZTA and DCC should have been defending themselves in court on manslaughter charges), cyclist inexperience (despite what the media reported, no experienced cyclist would ride where they could be hit by a car door), and an idiot in a car (the new facilities will have no effect on the latter on 99% or Dunedin’s roads). The comparison should not be made between the old lane or the current lane and the proposed separated cycle path, but between a properly designed lane (no car parks on the LHS of the road as cyclists have requested for >10 years!) and the proposed path. This hasn’t been done.
    There is no real reason why the lane can’t be on the LHS. The placement on the RHS of the road is flawed because 1) cyclists cycle on the LHS on all the other roads in Dunedin, so this decreases ‘predictability’ (“I thought the cyclist was on the left officer”), one of the prime factors in road safety, 2) intersections will require separate traffic light phases for cyclists due to the crossing of motorist/cyclist paths when turning – this will increase delays which is likely to increase the incidence of red light running by both cyclists and motorists (decreasing safety). If a barn dance-style crossing is used then merging cyclists will have increased danger of hitting other cyclists and delays will be even longer (see point 2), 3) the proposed barriers will not only inconvenience cyclists (because mid-block destinations on the opposite side of the road will become difficult to access – cyclists will have to bike past where they want to go, cross at the light, bike back on the opposite side of the road on the footpath) but lead to increased conflicts between cyclists and pedestrians who will also want to cross the road mid-block and who will shelter in the cycle lane.
    In addition, the lanes will require much reduced speeds by many cyclists (although just shy of 50, I often travel above 40 kph on the one-way – there’s always a tail wind in one direction!) due to the narrowness and inability to swing around slow cyclists. This and point 2 are likely to lead to displacement of cyclists to other routes.
    Furthermore, the “cycology” of this sort of cycle facility is never considered – we do not have a cycle safety issue in Dunedin, but a motor vehicle/motorist danger. Once we realise this, the way the problem is approached changes. Forcing cyclists off the the road and inconveniencing them rather than motorists (the cause of the problem) sends a major message: “whenever there is a conflict between cyclists and motorists, motorists do not have to do anything to change their behaviour”. No wonder all these millions of dollars spent have no effect on the number of cyclists killed and injured. The ‘share the road’ sign south of Port Chalmers does more for cyclist safety than these lanes ever will, because i alters motorist behaviour.
    These are the reasons why I voted ‘no’ to both options. I would have voted ‘yes’ to removing car parks from the LHS of the road and having a decent cycle lane which does not inconvenience cyclists in any way and costs a pittance in comparison.

    • Hank Weiss says:

      Dear Dunedin Biker:

      Thanks for your thoughts and comments. I agree wholeheartedly that the pre-existing lanes were poorly designed and inviting of a tragedy. However, I think it is incorrect to assume that cyclist experience was an important preventable factor in the recent death. In fact, Dr He was very experienced. He cycle-commuted almost every day to work and cycled for years in Australia and China before coming to NZ. It’s easy to say in hindsight that a victim (or even the door opener) should have been more careful, but aside from it sounding too much like blaming the victim, it harkens back to a notion that modern road safety is trying to move away from. Namely, human behaviour is hard to control and we all make mistakes or suffer lapses of concentration, even the most experienced among us. Instead, we want to design the transport system so that mistakes can be made, regardless of experience level, and people don’t pay for them with their lives.


      Buses are a key part of the decision to recommend a right-sided lane. They are quite common and at times heavily trafficked with those boarding and alighting. Recessing them into the footpath as you suggest, a dicey and expensive option, still leaves them merging back into and across the cycle lane. Quoting from the Working group options report:

      “There are a large number of bus stops along the links. The higher the number of buses stopping at stops, and the higher the number of passengers boarding and alighting, the more problematic it is to provide a cycle facility for the Interested but Concerned that works for both cyclists and bus passengers. The high degree of interaction between cyclists and bus passengers would cause safety concerns.”

      Right-side Placement

      I suppose there could be a small element of decreased ‘predictability’ to some drivers. But pedestrians are on the right side so drivers have already learned to look for conflicts on the right at intersections, therefore it’s doubtful this will much of a new factor. If this actually does leads to some degree of unpredictability, it may very well be balanced by the increased visibility of cyclists being next to the driver. The light phasing you refer to remains whether the protected lane is on the left or the right, so I don’t see how that impacts the decision. The thinking was also influenced by the very large left side driveway traffic at Countdown and New World.

      As to inconvenience to people on bikes because of perceived barriers to mid-block destinations, I believe you are neglecting two things. First, the simple alternative that cyclists can cross over before the destination and walk the half block on the foot path or ride the left hand lane after crossing at the previous intersection and riding to their destination, whatever makes them most comfortable. Secondly, it is quite possible the barrier design, whatever it is, will have extensive gaps (for drive-ways and drainage) and such gaps could theoretically be used at mid-block locations.

      I digress somewhat, but since you brought it up, mid-block pedestrian crossing on a 50K road shouldn’t be condoned, but we know it happens frequently. In fact, it’s inevitable when a stroad such as SH1 runs through the middle of the CBD, a poor planning choice in the first place. Personally, I feel NZTA should recognize this basic conflict and reduce speeds there to 30K and give us back our main street. You can’t have both a thruway (a road) and a multi-use main street thoroughfare (thereby creating a street-road or stroad), without creating significant conflicts between different types of users. If safety is paramount, which is what we always hear people say, then 30K is the way to go.

      What Values Do We Have

      Also, while the problem of a pedestrian temporarily sheltering in the cycle lane during a mid-block crossing could take place, it’s something that can occur with an unprotected lane as well. The more popular a lane is (and protected lanes are clearly more popular), the less likely that will happen.

      You have the right, of course, to choose what to support. But it is disappointing that you choose not to balance the advantages of the wider uni-directional lane, even for your type of riding. I agree with you that the bi-directional design dissuades safe passing and reduces the perceived level of service for high speed users such as yourself. These are mitigated by the uni-directional design and thus in my mind deserving of support between these two options.

      As to your concern that a protected lane could “force” advanced cyclists off the road, I think in practice that’s not really going to happen much. That doesn’t mean a few individuals won’t choose to take another route, that’s their prerogative, but once they experience the new infrastructure, most advanced riders will see the benefits. I think you will find, as most advanced riders have elsewhere, that the few compromises you might have to make sometimes, are outweighed by the safety and convenience of a protected lane and just as importantly, recognize the benefits they bring to potential riders not as confident as you or I. I am a very experienced rider and sometimes like to go fast, and have ridden in protected lanes in the US and Europe. They are simply a joy. There is much less to worry about and I have found it just fine to pass, be passed, and work around other users.

      That being said, there is no perfect solution for everyone. The diverse cycling community, if there is such a thing, needs to make some compromises as well. But most importantly, in practice, cities everywhere are finding the protected lane approach an important tool for reaching the huge group reluctant to take the risks inherent in the unprotected approach you espouse (see Pucher et al). That’s an important reason why the approach of just removing parking and having a wider unprotected lane, while a definite improvement, was not prioritized. As to costs, I am not so sure adding the barriers is that big a proportion of the costs because making a straight route through the existing parking, planters and curb extensions is where most of the remedial costs are likely to be.

      Lastly, I would like to see the evidence that any ‘share the road’ sign alters motorist behaviour. I know of nothing in the road safety cycling literature that has shown this to be the case.

      So I am genuinely sorry we didn’t get your vote. We certainly got a ton from people of all types who cycle and people who want to cycle. You and I have much in common the way we view the hazards. If option 1 goes forward, I would be happy to hear from you in three years how you like what is there. If I am wrong, you will have my apology for your inconvenience, even if it benefits many other riders and makes everyone safer. If I am right, I’ll be happy to be invited to a cup of ‘jo’ to jointly toast a great step forward for all of Dunedin.

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