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Tag Archive for: bikeway study

Crowd of bicyclists

Bikeway Study: Strategies to Improve Bicyclist Safety

July 31, 2020/3 Comments/by Mighk Wilson

 In Part One of this series, I discussed how most bikeway studies fail to address the key factors that lead to crashes, and I described the basic findings of Metroplan Orlando’s new bikeway study. Part Two went into deeper detail to show how cyclist direction, position and speed affect crash risk. In this final part, I’ll discuss how data from the study should inform attitudes and strategies to improve cyclist safety.

Crowd of bicyclists

Jacobsen’s widely-cited study

In a 2003 paper in Injury Prevention [1], Peter Jacobsen found that higher bicycle use went with lower cyclist crash rates across geographies (European nations and California cities) and over time (United Kingdom and The Netherlands). As cycling (and walking) increased, it seemed that the overall crash risk dropped. In the discussion section of the paper, Jacobsen wrote:

“It seems unlikely that people walking or bicycling obey traffic laws more or defer to motorists more in societies or time periods with greater walking and bicycling. Indeed, it seems less likely, and hence unable to explain the observed results. Adaptation in motorist behavior seems more plausible and other discussions support that view.”

Though Jacobsen provided no behavioral data to support this explanation, it has become popular among bikeway proponents. When skeptics point out conflicts created by many bikeways, advocates have a handy response: “But there’s safety in numbers…” Others have questioned Jacobsen’s math [2].

Does Jacobsen’s conclusion hold water?

Our bikeway study shows whether that assumption holds water. Did rates for motorist-caused or bicyclist-caused crashes increase or decrease with larger numbers of bicyclists?

I divided the twenty streets into five groups of four each, ranked from lowest to highest bicyclist counts over 10 years. The table below shows enormous differences in the amount of bicyclist travel. There was 60 times as much bicycle use on the busiest streets as on the least busy.

Quintile Streets by Bicyclist ExposureLowest Quintile2nd Quintile3rd Quintile4th QuintileTop Quintile
Bicyclist Miles Traveled819,0005.344 M9.674 M13.341 M49.218 M
Miles Between Motorist-Caused Crashes19,00046,00039,00049,00045,000
Miles Between Bicyclist-Caused Crashes13,00073,000125,000205,000198,000

I left the lowest 1/5 out of the analysis, because the bicyclist exposure and the numbers of crashes are tiny. Even from the second group to the top group, there’s a nine-fold increase in bike use:

Orlando bikeway study: miles between bicyclist- vs motorist- caused crashes
The results? There is little difference in the risk of motorist-caused crashes. (Remember, a higher number — more miles between crashes — means lower crash risk.) But bicyclist-caused crashes were 170% to 180% lower for the top and fourth quintiles!

Better overall bicyclist behavior is responsible for the “safety in numbers” effect. [3]

It’s plausible that motorist behavior improved some small amount on the higher usage streets, but that would probably be masked by the reduced risk due to slower cyclists on the sidewalks.

Three of the four streets in the 4th quintile (with the lowest risk for cyclist-caused crashes) are two-lane streets with bike lanes. These are just the type of streets touted as “bike-friendly.”  Bikeway advocates like to say that bikeways attract potential cyclists who are “interested but concerned.” [4] Wouldn’t “interested but concerned” cyclists generally be more cautious and less likely to cause crashes?

The streets in the top quintile are all high-speed, high-volume, four- and six-lane arterials. Their obvious risks should encourage cyclists to use extra care.

It’s possible that motorist behavior does improve with still higher bicycle use. On the busiest cycling streets in the Orlando bikeway study, a bicyclist would pass any given point about once every eight minutes. In some European cities, bicyclists are almost always in sight. Motorists’ expectations would be radically different there.

Study results: crash risks and numbers

Orlando bikeway study: key to the three graphs below

Key to the three graphs below

In this bikeway study, ten times as many cyclists were using bike lanes on the bike lane streets as were using the travel lanes on the comparison streets. Almost all bicyclists on the comparison streets were riding on sidewalks. But there was only 28 percent more bicyclist travel overall on the bike-lane streets. Most of the increase in bike lane use was due to bicyclists switching from the sidewalk to the bike lane.

Orlando bikeway study: Estimated miles of travel on streets with and without bike lanes

Though the bike lanes in this bikeway study presented a 53 percent lower crash risk per cyclist, four times as many motorist-caused crashes occurred in bike lanes on bike-lane streets as in travel lanes on the comparison streets. Almost all of the motorist-caused crashes on the comparison streets, and more than 3/4 of them on bike-lane streets, occurred on sidewalks and crosswalks.

Orlando bikeway study: Counts of motorist-caused crashes on streets with and without bike lanes

The crash rate was higher for sidewalks on the bike-lane streets than on the comparison streets, and so the bike-lane streets had a higher overall crash rate, despite the 53 percent lower crash risk than with the travel lanes on comparison streets. (Recall that a longer bar in the graph below represents a longer mileage between crashes — lower crash risk.)

Orlando bikeway study: miles between motorist-caused crashes on streets with and without bike lanes

How to approach a Vision Zero goal

The stated goal of the Vision Zero Network is to eliminate all traffic fatalities and severe injuries, while increasing safe, healthy, equitable mobility for all. [5]

In order to truly approach this goal, much more effective risk-reduction methods than bike lanes and sidepaths must be implemented. As I highlighted in Part 2:

Rather than bikes lanes or sidewalks improving the safety of bicyclists, bicyclists are improving the safety of bike lanes or sidewalks by riding slower.

Bikeway advocates point to separated bike lanes, special bicycle signals, and channelized (“protected”) intersections as improvements over sidewalks and ordinary striped (“basic”) bike lanes. Slowing bicyclists at the approaches of intersections is part of bikeway designers’ design strategy, and may reduce risk somewhat.

In our Metro Orlando data, though, only 28 percent of motorist-caused turning and crossing crashes (for cyclists riding with the flow) occurred at signalized intersections. Forty-two percent occurred at unsignalized intersections (mostly minor cross streets), and 30 percent at driveways.

Orlando bikeway study: turning and crossing crashes by intersection type

Most turning-movement collisions do not occur at signalized intersections. It is not practical to install preventive measures everywhere a motorist may cross the path of a bicyclist.

Mitigating all conflicts would require channelization to slow bicyclists at every intersection and driveway. This would be very costly — if even possible — and would slow cyclists nearly to pedestrian speeds, making bicycling less useful. [6]

Cyclists who tried to maintain their preferred speed could be blamed for crashes in the bikeways, or harassed for using lane control in the travel lanes. Now with electric-assist bikes, novice cyclists can ride on bikeways at the speeds of fitter, experienced cyclists. This is not a good combination.

The 6 E's of a bicycle program

Final Thoughts

The real world is a very messy place. As with many of life’s other challenges and questions, prevention of bicyclist crashes doesn’t lend itself to simple, straightforward answers. Nor does the question of whether bikeways really improve cyclist safety.

Cyclist skill, direction, position, speed, predictability, and conspicuity are concerns in crash prevention. So are motorist attention, speed and turning movements, lighting conditions, sight lines, traffic controls, and many other lesser concerns.

Attempting to address all of these factors with street and bikeway design is bound to fail. Design can improve safety, but it won’t get us as far as we’d like.

“Prepare the child for the path, not the path for the child.”

This saying (perhaps Native American) has been replaced with a popular version, found on parenting websites, using the word “road” instead of “path.” [7] and [8]

Prepare the child for the road, not the road for the child. Adults as well as children benefit from such a philosophy. Bicyclist training and education are not optional.

Mother and child riding side by side on a street and both signaling a right turn


Footnotes

[1] Jacobsen’s article

[2] The widely cited hyperbolic, descending curve which appears in every graph in Jacobsen’s report  is an artifact of faulty math. Correct math gives varied results. See this for an explanation.

[3] Other research has also shown that bicyclist crash rates are lower on busy streets, notably a  study by William Moritz from the 1990s. One factor: cyclists with more experience and greater skill are more likely to ride on busy streets. Also, more mentoring occurs where bicycling is more common. See discussion here.

[4] This categorization, one of four by Portland, Oregon bicycle coordinator Roger Geller, conflates two characteristics. Not all interested people are concerned, and vice versa.

[5] Wikipedia article describing Vision Zero, with links to other resources.

[6] The reduction in possible trip destinations within a given time is greater: in an urban grid: half the speed, 1/4 the destinations.

[7] See this, for example.

[8] However, Strong Towns offers the opposite advice.

https://cyclingsavvy.org/wp-content/uploads/2020/07/crowd-of-bicyclists1-702.jpg 468 702 Mighk Wilson https://cyclingsavvy.org/wp-content/uploads/2021/06/CS-logo_xlong-header.png Mighk Wilson2020-07-31 12:55:472020-08-02 13:08:58Bikeway Study: Strategies to Improve Bicyclist Safety

Bikeway Study Part Two: Your Speed, Your Choice

July 24, 2020/19 Comments/by Mighk Wilson

Safer Motorists or Safer Bicyclists?

Last week, in the first of a three-part series describing my research on bikeway crash risk, I gave relative estimated risks for three types of motorist-caused crashes when bicyclists rode with the flow…

miles between crashes graph_intersection with diagram

Travel Lane Edge – 61,000 Miles Between Crashes (Highest Risk)

Bike Lane – 75,000 Miles

Sidewalk – 122,000 Miles (Lowest Risk)

… and asked:

Why would the risk be lowest for bicyclists riding on sidewalks?

All crashes occurred at intersections and driveways with no sort of “protection” for the bicyclist. Don’t experienced bicyclists avoid using sidewalks — and sometimes even bike lanes — because riding in the street is supposed to help them avoid such conflicts?

Stay with me while I show you where the data led me as I pondered this question.

There are two key possibilities why these risks are lower: (1) Motorists might be more likely to yield to bike lane and sidewalk cyclists for some reason, and (2) Bike lane and sidewalk cyclists might be better able to avoid a motorist-caused crash.

It’s often argued and assumed that striping a bicycle lane leads motorists to look for and yield to cyclists. But the sidewalk cyclists had lower risk for these motorist-caused crashes than even the bike lane users, though sidewalks are neither designated nor designed for use by cyclists.

When we split up the crashes further, we see that only the risk of drive-outs is higher for bike-lane and sidewalk cyclists.  Right-hook and left-cross crashes are less likely:

Right Hook & Left Cross

miles between crashes graph_right hook and left cross

Travel Lane Edge – 73,000 Miles (Highest Risk)

Bike Lane – 100,000 Miles

Sidewalk – 300,000 Miles (Lowest Risk)

Sidewalk cyclists have the highest risk of drive-out crashes:

Drive-Out

miles between crashes graph_drive out

Travel Lane Edge – 367,000 Miles (Lowest Risk)

Bike Lane – 292,000 Miles

Sidewalk – 245,000 Miles (Highest Risk)

Would motorists be more likely to yield to bike lane and sidewalk cyclists during overtaking right turns and opposing left turns, but not during drive-outs? I think that this is not more likely.

People Make Mistakes

News Flash: Humans make mistakes, whether they’re walking, bicycling, or driving motor vehicles.

We expect slower automobile and motorcycle drivers to be better able to react more quickly than faster ones to avoid conflicts caused by other motorists.

Why would we assume differently for bicyclists? [1]

Recall the average speeds we found for cyclists using the three positions. A slower cyclist needs less perception and reaction time and less braking distance:

Bicyclist PositionBicyclist Average (Mean) SpeedBicyclist 85th Percentile SpeedStopping Distance at 85th Percentile Speed
Travel Lane14.5 MPH18.4 MPH104 Feet
Bike Lane11.8 MPH15.7 MPH83 Feet
Sidewalk9.3 MPH12.4 MPH60 Feet

Facing an impending motorist-caused crash, the bike-lane user riding at the 85th-percentile speed would need an additional 23 feet of stopping distance compared to the sidewalk rider — about the width of the typical two-lane street. The difference is about the same between the travel lane and the bike lane. The total difference between travel lane and sidewalk is about the width of four traffic lanes, or 44 feet.

85th Percentile Bicyclist Speed and Stopping Distance

85th percentile stopping distance

With right-hook and left-cross crashes, the motorist is coming from the bicyclist’s left, so the farther right the bicyclist is, the longer it takes for the motorist to reach the bicyclist’s path. This means that the bike lane or sidewalk bicyclist gets more reaction time. With drive-out crashes, the travel lane cyclist gets the most reaction time.

Rather than bikes lanes or sidewalks improving the safety of bicyclists, bicyclists are improving the safety of bike lanes or sidewalks by riding slower.

The Takeaway

If you’re going to ride on the sidewalk, bike lane or edge of the travel lane, you must ride slower.

I can’t tell you how slow is slow enough. But if you’re having more close calls with turning and crossing vehicles than you’d like, you need to either slow down, or use lane control. [2]

Based on the data, each additional mile per hour of bicyclist’s speed increases the risk of a motorist-caused crash about 9 percent.

With lane control, you give yourself much more reaction time for drive-out crashes, you eliminate the right hook crash, and you get more options for avoiding the left cross.

lane control allows faster speed

To put it in the simplest of terms: The faster you go, the more important it is for you to control your travel lane.

Sidepaths and Motorist-Caused Crash Risks

We performed the same type of analysis for five sidepaths which have been in place for over ten years. I was curious as to whether they would have better safety performance than a regular sidewalk. They did — about 68 percent better, on average — but it varied widely. Looking closer, I found that three of the paths had few intersections and commercial driveways — 4.6 per mile — while the other two had 11.6 per mile. Low-conflict paths had 64 percent lower motorist-caused crash rates compared to the other two paths; 51 percent lower than for ordinary sidewalks.

Low-Conflict SidepathsHigh-Conflict SidepathsRegular Sidewalks
Intersections and Commercial Driveways per Mile4.611.610.5
Cyclist Miles Between Motorist-Caused Crashes81,000 (Lowest Risk)29,000 (Highest Risk)40,000

miles between crashes graph sidepaths

Notice that high-conflict paths had 10 percent more intersections and driveways per mile than the sidewalks, but 38 percent higher motorist-caused crash risk, likely due to the higher bicyclist speeds on the paths (16.3 MPH versus 12.4 MPH for the sidewalks).

If we replace a sidewalk with a sidepath without somehow reducing the turning and crossing conflicts, the risk for the bicyclists will likely increase. This information helps you as a cyclist to decide when a sidepath might be reasonable to use — such as going with the flow on a low-conflict path — and when to avoid one — for example, when going against the flow, or going with the flow fast on a high-conflict path.

Bikeway designers can’t foresee every situation for you, so don’t expect them to.

Next time: Safety in numbers, Vision Zero, and “Preparing the Child.”

Footnotes

[1] The 1976 Bikecentennial study found that 38% of crashes occurred on downgrades, though the constituted only 15% of the route. This was for all types of crashes.

[2] This short video explains lane control and the need for it.

https://cyclingsavvy.org/wp-content/uploads/2020/07/85th-percentile-speeds-feature-1.png 353 349 Mighk Wilson https://cyclingsavvy.org/wp-content/uploads/2021/06/CS-logo_xlong-header.png Mighk Wilson2020-07-24 11:55:302021-07-29 14:29:14Bikeway Study Part Two: Your Speed, Your Choice

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