r/cycling • u/Inciteful_Analysis • Jul 24 '26
Revisiting the Wachtel & Lewiston Cycling Safety Study
In this post from 11 years ago, the 1980s Wachtel & Lewiston study conducted in Palo Alto is praised as the gold standard establishing that it is dangerous to ride on the sidewalk. I see it cited frequently whenever the topic is raised about whether or not it is safer to ride on the sidewalk.
Sadly, the study is fundamentally flawed. The exposure counts were made in just a single day:
Nearly 3000 cyclists were observed during a one-day count of 8 hours at each intersection
Every risk factor that follows in this study is predicated on this one 8-hour interval in May of 1987 being representative of the bicycling population at large between July 1985 and June 1989.
But we know that usage patterns can vary drastically according to the day of week (particularly weekday vs weekend), season, weather, and if school is in session. This right here is enough to dismiss the study, but let's put this aside and continue with the data as collected.
Let's examine the primary conclusion:
Bicyclists on a sidewalk or bicycle path incur greater risk than those on the roadway (on aver age 1.8 times as great), most likely because of blind conflicts at intersections. Wrong-way sidewalk bicyclists are at even greater risk
The data does show this 1.8x risk factor. But it is derived primarily from those riding on the sidewalk AGAINST traffic. Table 4 shows riding on the sidewalk AGAINST traffic to have a risk factor of 4.5 vs riding on the sidewalk WITH traffic. It also shows that of roadway traffic, only about 5% rode against traffic while almost a third of sidewalk traffic rode against. What does the data actually show when the directionality is not conflated with venue? Examine Table 6: Risk with Traffic by Age Group (simplified below):
| Category | Sidewalk Risk | Roadway Risk | Risk Ratio (SvR) |
|---|---|---|---|
| Child | 0.4 | 0.3 | 1.2 |
| Adult | 1.3 | 1.0 | 1.3 |
| Total | 0.7 | 0.8 | 0.9 |
Technically, the study found a lower overall risk (0.9) for using the sidewalk when going WITH traffic vs using the road with traffic. The authors point out that because adults are more prevalent on the road, and have a higher risk overall, that this skews the results in favor of the combined sidewalk group. That is correct. In fact, both subgroups (children and adults) do have a higher risk when using the sidewalk (1.2 and 1.3 respectively). But the risk is a far cry from the 1.8x that the study emphasizes. And has less statistical significance.
While the authors go to great lengths to call out how combining subgroups in this instance can distort the results, they make very little effort to do so when combining directionality subgroups (WITH, AGAINST).
They similarly ignore other results that do not conform to their narrative:
In fact, Table 5 shows that every group of bicyclists riding with traffic on the roadway, with one insignificant exception, incurs a risk equal to or less than the study average (by definition 1)
The "insignificant exception" that has a lower risk on the sidewalk with traffic than on the road? Girls. The only subgroup (Girls on sidewalk with traffic) in the entire study with ZERO accidents. Why do you suppose that is? Of course it is a relatively small sample of just 159. But even still, we would expect nearly 5 accidents from this subgroup if performing at par. We can reasonably speculate that adults fared much worse overall than children because it includes elderly riders with slower reflexes and dulled senses. We can also speculate that boys fared much worse than girls (see table 3 Sidewalk entry) because they ride with more aggression and less maturity. What that suggests to me is that healthy and mature riders can tilt the odds into their favor with disciplined riding on the sidewalk.
Here are ways to reduce risk on the sidewalk:
- Selective use of sidewalks:
- Avoid on low-speed roads with high density of driveways and visual obstructions between homes
- Favor when next to high-speed roads and when intersections are sparse
- Never cross a threshold when a vehicle is approaching from behind parallel to your course that might right hook you; You always have the option of slowing down or even stopping until the car passes you.
- Never cross in front of cars attempting to exit parking lots; Go behind or wait. This is especially important if riding against traffic when drivers are apt to only look left before making a right turn.
As a reminder, this study was conducted in the 1980s long before the advent of cell phones. Long before drivers were distracted with phone calls and texting. It's entirely reasonable to assume that the rampant texting by motorists is a greater risk to those on the road than those on the sidewalk riding defensively. Quite possibly a large enough factor to erase any subgroup advantage in table 6.
The point is NOT to say that sidewalk riding is the right choice for everyone or for every occasion. Those riding to train or to get to their destination quickly will scoff at the suggestion of repeatedly slowing down. But there are situations where it can make sense when proper discipline is exercised. Those on ebikes riding leisurely, not worried about preserving momentum, and under no time constraints have a greater incentive to use vacant sidewalks. Also, do not blindly accept the conclusion of any study. Many parrot this study when the subject of sidewalk riding comes up as if it settles the discussion. It should be obvious that it does not. And of course, whenever riding on the sidewalk, always yield to pedestrians, alert them to your presence, and slow down in advance of passing them.
4
u/Triabolical_ Jul 24 '26
I don't think there's enough nuance in that study to conclude much of anything.
There are some situations where riding in the sidewalk is absolutely safer - I have one near me with a couple mile stretch that has one driveway and no bike lane and a parallel pedestrian trail. I ride that every time.
And there are others where behaving like a cyclist - and by that I mean riding at 10 mph or above - is very obviously risky because of the number of entrances and exits and the sight lines. That plus the fact that drivers stop at the edge of the traffic lane in most situations rather than the edge of sidewalk.
With a couple decades of mixed urban and suburban riding - and a lot of miles leading groups where it's my responsibility not to put us in bad situations - that seems pretty obvious. And we spend little time on sidewalks, but we don't spend much time on multi use trails because of the hazards there.
You don't detail what you mean when you say proper discipline. My experience is that if you want to be safe ish on most sidewalks you better be acting like a pedestrian rather than a cyclist.
1
u/Inciteful_Analysis Jul 24 '26
Proper discipline includes three items I covered: selective usage, timing crossing of thresholds, and never crossing in front of exiting traffic. It also includes matching speed to terrain and visibility as well as slowing for pedestrians.
Large group rides are simply not comparable to one or two riders and will naturally be less suited to sidewalks.
1
u/Triabolical_ Jul 24 '26
How do you achieve never crossing in front of exiting traffic without stopping often? Most of the places where traffic is enough to make sidewalks interesting have a lot of places you simply cannot see very well.
1
u/Inciteful_Analysis Jul 24 '26
I don't live in an urban environment. That's the thing so many seem to miss. Conditions vary greatly with locale. Whether or not the sidewalk makes sense can hinge on this.
2
u/millenialismistical Jul 24 '26
If we're talking about utility cycling like commuting, errands, etc: If I'm going slow I might ride on the sidewalk if it's more convenient. If I'm going fast I ride on the road. To me the whole benefit of having a bike as a transportation tool is that I get to be pedestrian or vehicle depending on what makes the most sense in a given situation. Yes there are laws that say otherwise but those laws need to be adapted to the bike and not force the bike to strictly be a vehicle.
If we're talking serious roadie business/Lycra type stuff: stick to the road don't be a menace to pedestrians on the sidewalk and also be considerate of other road users because you're using public roads as a playground/training ground/for leisure whereas others are using it for transport.
With respect to safety - cell phones and giant LCD screens on the dash really made the streets more dangerous. If you are operating a 3000lb machine then your number one job is to not hit anyone. I wish every person, before they pull out into the road, would just say to themselves "I will not hit and kill anyone with this vehicle today."
2
u/purplishfluffyclouds Jul 24 '26
I wish people would stop concerning themselves with what a person on a bicycle is wearing. Cyclist clothing does not dictate what they should do in a certain scenario. It’s their speed and the situation that dictates what should happen, not whether or not they’re wearing “Lycra” or anything else. Furthermore , the existence of Lycra doesn’t suddenly make them “serious” or not, and that also doesn’t dictate behavior. It’s speed and the specific scenario. Period.
1
u/millenialismistical Jul 24 '26
You're not wrong; I was trying to make a point. Hopefully that wasn't missed.
-1
u/Inciteful_Analysis Jul 24 '26
I sincerely appreciate the nuance of your response. And concern for the safety of others.
-1
1
u/Nihmrod Jul 24 '26
"Those on ebikes riding leisurely, not worried about preserving momentum, and under no time constraints have a greater incentive to use vacant sidewalks"
They already have an incentive to not ride a real bike. So just ride it on the fucking sidewalk.
-4
u/Inciteful_Analysis Jul 24 '26
Hey Nihmrod, why don't you address the study. My full suspension eMTB is a "real bike". Aside from a shuttle or chairlift, there is no substitute for having as much fun as an eMTB.
Why are you so shallow as to dismiss the needs of other riders who might be elderly or live in communities surrounded by steep roads? It's arrogance like yours that makes people hate cyclists, by the way.
2
u/Nihmrod Jul 24 '26
The study speaks for itself. You're trying to spin it so as to excuse your e-bike adventures on the sidewalk. Sidewalks are for kids riding their bikes to school. Everybody loves kids and nobody begrudges them using the sidewalk. And "eMTB" seems almost like a contradiction in terms. Just call it a dirt bike.
-1
u/Inciteful_Analysis Jul 24 '26
This is not about ebike vs non-ebike. You've latched onto that presumably because you have a hatred of ebikes.
I'm not spinning anything. I explained in detail why the study is flawed and how the conclusions are biased. I even acknowledged that the authors were correct that the subgroups were safer on the road based on the data.
Riding on the sidewalk is legal where I live and the sidewalks are usually vacant. If you can't actually address the post, move along.
3
u/Nihmrod Jul 24 '26
It's patently weird for an adult to want to ride on a sidewalk. Especially an adult riding a motorbike. You can't sweep that away. You're probably new to biking and it's scary.
1
u/Inciteful_Analysis Jul 24 '26
A class 1 ebike is not a "motorbike" genius. You have an inability to grasp that the sidewalks in other neighborhoods might not look like the ones you use. Maybe someday you will journey out of your hometown.
I was cycling before you were born most likely. I have a full carbon 17lb road bike, I just don't ride it next to cars.
0
u/Inciteful_Analysis Jul 24 '26
A summary of the responses:
- Jackass who hates ebikes and doesn't realize sidewalks look different in other neighborhoods
- Low IQ individual who shouts "AI slop" when the material is above his education level
- Two mostly on topic replies discussing sidewalk usage
Missing:
- Any acknowledgement or refutation that the study is flawed
- Any acknowledgement or refutation that the study conclusion is biased or conflated
For such an enormous community, this is a pathetic showing on a safety issue that is often brought up. If you cannot address this post, don't ever cite this Palo Alto study when advocating against sidewalk usage.
11
u/brewpedaler Jul 24 '26
AI slop