Author: DOUG DAHL

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Bicycle Question Round-up Part 2

It’s time for bicycle question round-up part two. You’ve been asking a lot of questions about where bikes should ride; bike lane, sidewalk, or roadway. Let’s take a look at what’s legal, and what’s smart.

1. Is it legal to ride a bike on the sidewalk, and if so, who has the right-of-way? How about switching between the street and the sidewalk?

Riding a bike on the sidewalk is usually legal, and for a few cyclists it might be the right choice. When riding on the sidewalk, a cyclist is required to yield the right-of-way to pedestrians. For young cyclists that don’t have the confidence or experience to ride in a bike lane or on the street, riding on a sidewalk makes sense. It’s safer, and really, a five-year-old that’s just learned to ride doesn’t travel much faster than a pedestrian. I can also think of a couple situations when experienced cyclists might choose a sidewalk over a road. When traffic conditions are dangerous the sidewalk might be the safest choice, and on a steep hill without a bike lane, a cyclist riding at a slow pace might move to the sidewalk for safety, and also to open up the roadway for traffic. Continue reading “Bicycle Question Round-up Part 2”

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Pinky

Read this before watching: In this video you’ll see some people making a gesture with their pinky fingers. For the typical Northwest Washington resident, that gesture doesn’t have much meaning. But in Australia, where this was broadcast, that’s what you do to imply that a person (a male person, to be specific) has a remarkably small, well, this is a family-friendly site, so small package.

Now you’re ready to watch this traffic safety PSA.

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BAC Calculator

A Blood Alcohol Concentration Calculator is a helpful tool for estimating BAC, but don’t rely on it for an accurate personal measurement. This calculator factors gender, weight and rate of consumption, but many other factors affect BAC and impairment: Age, fat/muscle content, metabolism, emotional state, medications, food, carbonated drinks, diabetes, alcohol intolerance and drinking history all influence alcohol’s effects. Alcohol impacts each individual differently, and even the same individual will experience different effects depending on changes in influencing factors. When it comes to alcohol and driving, the best approach is to avoid driving after you drink. Continue reading “BAC Calculator”

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Risk Takers Live Longer (And Other Methods of Understanding Data)

I’m going to generalize here: for most people the car is the default mode of transportation. Congratulations to all of you who read that and thought, “Well, that’s not true for me.” That probably means walk or ride your bike (unless your default mode of transportation is boat or plane- In that case, congratulations on being a total outlier), and you’re probably also in better shape than the people for who it is true. But are you safer?

If you have a fear of flying, you’ve likely been told uncountable times that flying is safer than driving. And that’s true. But how much safer? And what about other types of transportation? Rather than just provide a bunch of numbers, I’ve put together some graphs to help visualize the data. For some categories the answer is clear. (Hint: no matter how you look at it, flying on a commercial airline is the safer than driving a car.) However, other categories depend on what you measure. For example, cycling is more dangerous than driving, but cyclists live longer. What? Let’s look at the data and try to make some sense of it.

First the basics. Let’s start with this chart that lists various modes of transportation, along with the annual fatalities for each mode.

Fatalities by Transportation Mode

While somewhat informative, it only tells part of the story. If we only look at total fatalities we could reach some unexpected conclusions. Is a private pilot just as safe as a passenger on a commercial jet? Is riding a motorcycle 4 times safer than driving a car? If so, why don’t we wear helmets when we drive? Is it really safer to go boating than go for a walk?

Just counting total fatalities doesn’t factor in the exposure involved in the mode of transportation. What does that mean? Let’s imagine that there is a completely insane sport called “solo skydiving without a parachute”. I’ve seen some videos of crazy people jumping out of airplanes without parachutes, but they jump with friends they trust and they hook together during freefall. (https://www.youtube.com/watch?v=lDBrdl2sZWs Bonus: it includes a shameless Red Bull plug.) The sport we’re imagining doesn’t involve jumping with friends. You can guess how that might turn out. Let’s compare our fictitious sport with the actual sport of skydiving:

Skydiving Fatalities

If this chart provided our only information comparing our two kinds of skydiving, we could conclude that skydiving with a parachute is more dangerous than skydiving without one. We’re missing an important piece of information that’s preventing us from reaching an accurate conclusion. Here’s what we should be asking: How many people participated in each kind of skydiving? As it turns out, in 2013 skydivers made 3.2 million jumps. Of all those jumps, 24 resulted in fatalities. In our made up version of parachute-less skydiving there were 9 fatalities. But if we know that only 9 people participated we can make a much more informed decision about the risk. Based on what we know now, here’s what our comparison looks like:

1000 Skydivers

Okay, enough of the half-made-up scenario. Let’s look at some real comparisons. In the world of traffic safety, exposure is usually measured in fatalities over miles traveled. This method tries to create a more balanced understanding of the risks of various modes of transportation. In the skydiving example, the first chart could mislead someone (that someone would have to be detached from reality) into thinking that skydiving without a parachute is safer than with a parachute. The second chart clears that up. So let’s do the same thing with transportation. This chart breaks down common modes of transportation by fatalities per 100 million miles traveled.

Fatalities by miles traveled

Hold on a minute. I just got sidetracked making this graph. Look at that bar for motorcycle fatalities. I knew it was dangerous, but wow, that’s 25 times more fatalities than cars. I don’t feel like I’m taking as much of a risk on my bike now.

Okay, back to the topic at hand. Using miles as our reference for exposure works great to compare the same mode of transportation from year to year. If fatalities increase a bit, but the total miles driven also increases, we could reasonably conclude that the increase in fatalities was due to more drivers rather than worse driving behavior.

But comparing different modes of transportation by miles traveled can be misleading. According to that chart, driving in a car is much safer than riding a bike. That’s because the method we’ve chosen to use for exposure, miles, is heavily weighted to favor methods of transportation that cover a lot of miles in a short amount of time. Just look at the data for flying. There are so few fatalities per 100 million miles that it doesn’t register on the chart. If we instead selected our exposure measurement as time instead of miles to make our comparison, the results would look something like this:

Fatalities over time

Using time evens out the risk. (Unless you’re on a motorcycle.) Flying is still safer than driving in a car, but only about 8 times safer, rather than 420 times safer. And riding a bus becomes the safest form of transportation, barely ahead of commercial airlines. Based on miles traveled, cycling is nearly 7 times more dangerous than driving, but based on time, it’s just over 3 times the risk. Which method is better? Maybe that depends on what you’re trying to prove. Before we move on, I should note that it is unusual for data analysts to measure fatalities over time, so the data in this chart is somewhat subjective. Here are some assumptions used to make the calculation from miles traveled to hours traveled:
Average speed of commercial airline: 500 MPH (I know they measure in knots, but I converted it for consistency.)
Average speed of motor vehicle: 32 MPH – Based on an estimate from the US Department of Transportation
Average speed of a cyclist: 10 MPH – Based on estimates from a NCBI study

Now let’s go one step further, or in this case maybe one pedal stroke. One of the primary reasons people in the US give for why they don’t ride a bike is that it’s too dangerous. Using the data we’ve covered so far, that might be a reasonable conclusion. But we’ve based that conclusion entirely on one risk factor. Researchers with the National Center for Biotechnology Information evaluated what would happen if drivers replaced their short trips with cycling, estimating 7.5 kilometers (4.6 miles) a day on the bike. Here’s what they concluded:

Crash risk: The NCBI researchers concluded that based on miles traveled, there are 5.5 times more cyclist deaths than car occupant deaths. That number is a bit more optimistic than our roughly 7 times, as shown in the “Average Annual Fatalities Per 100 Million Miles” chart, but higher than our “by the hour” estimate. Based on the NCBI numbers, crash risk reduces the average life expectancy by 7 days.

Pollution: Even though drivers are exposed to slightly more pollution than cyclists, because of the increased breathing rate caused by exercise, cyclists inhale roughly double the pollutants. Surprisingly, pollution ends up as a greater risk than crashing, resulting in a 21 day reduction in life expectancy.

Exercise: Replacing car trips with bike trips is good for our health, in spite of the risks of crashing and pollution exposure. The NCBI study  puts that benefit at 8 months gained in life expectancy. A more recent study from the US National Institutes of Health estimated that the amount of exercise that the NCBI study used for their calculations would result in a 3.4 year increase in life expectancy. To be consistent we’ll stick with the NCBI numbers. Here’s what it looks like:

Car vs Bike Life Expectancy

By evaluating the overall risk of replacing car trips with bike trips, I’m inclined to want to ride my bike a bit more.

You may have noticed that I didn’t include many exact numbers with charts in this post. Data can be interpreted a variety of ways, as we’ve seen, and the goal here wasn’t to provide hard numbers but to give some perspective on driving risks. Using other data sources would have had a slightly different outcome, but the overall concept would have remained.

Finally, all that data fails to capture the most important factor in transportation safety; the individual behaviors of travelers. As a motorist, a cyclist or a pedestrian, I can greatly decrease my personal risk of injury or death by being aware of my situation and obeying traffic laws. We get data by looking at large quantities of numbers. Reckless travelers drive the numbers up, while safe travelers move them down.

I hope you’ve enjoyed what is admittedly a data-driven post, because there will be more. Coming up next: The Most Dangerous State to Drive (and some guesses about why).

Note: I searched through a lot of data to put this together, and I want to thank all the researchers who make this information available. Here is a list of websites that helped develop this article:

http://www-fars.nhtsa.dot.gov/Main/index.aspx

http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/entire_02_2014.pdf

http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/index.html#chapter_2

http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_02_01.html

http://www.rita.dot.gov/bts/sites/rita.dot.gov.bts/files/publications/national_transportation_statistics/html/table_02_04.html

http://static.mgnetwork.com/rtd/pdfs/20110610_deathrates11.pdf

http://journalistsresource.org/studies/environment/transportation/comparing-fatality-risks-united-states-transportation-across-modes-time

http://www.vehicularcyclist.com/comparat.html

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2920084/

http://bicycleuniverse.info/transpo/almanac-safety.html

http://www.caranddriver.com/features/safety-in-numbers-charting-traffic-safety-and-fatality-data

http://journals.plos.org/plosmedicine/article?id=10.1371/journal.pmed.1001335

Icons made by Freepik from www.flaticon.com is licensed by CC 3.0 BY
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Crosswalks – Part 1

Q: Crosswalks Part One: Can you please explain crosswalks, and when motorists are supposed to stop, including unmarked crosswalks?

A: Ah, yes, crosswalks. On the surface it seems so obvious; when a pedestrian is in a crosswalk, drivers should stop. But there’s more to it than that, including the question, “What is a crosswalk?” Until I read the definition of a crosswalk in the Revised Code of Washington years ago, I thought a crosswalk was the white paint on the road that pedestrians used to get across intersections. While that is a crosswalk, it is not the only kind. When you approach an intersection and see the stripes just beyond the stop line, you’re seeing a marked crosswalk. However, if you were to come to an intersection without the painted crossing markings, you’d still be approaching a crosswalk, but in this case it would be an unmarked crosswalk. Confused yet? Just remember that painted on the road or not, that ten foot wide strip between where you’re supposed to stop at an intersection and where the lanes of travel cross over each other is a crosswalk. Continue reading “Crosswalks – Part 1”

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Escape From a Texting Driver

Q: The person driving behind me is obviously texting… I can see the top of their head for 10 seconds at a time in my rear-view mirror. If I speed up over the speed limit to put some space between myself and the texter, will the officer who pulls me over understand?

A: I’m getting into some dangerous territory trying to answer this question, as you’ve asked me to respond on behalf of the law enforcement officer that might stop you if you speed to get away from that bonehead driver texting behind you. I don’t think I can make that prediction, so I’m going to take a different approach. We’ve heard a lot about distracted driving and the increased risk of collisions. Current studies indicate that a texting driver is as at least as serious a risk as an impaired driver. I know when I’ve been driving near what appears to be a drunk driver, I give myself some distance. And call 911. Continue reading “Escape From a Texting Driver”

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Bicycle Question Round-up, Part 1

Welcome to the bicycle question roundup. Questions about bicycles have been pouring in, and I’m going to try to tackle them several at a time, so this is part one. I don’t usually edit the questions much, but some of these had a strong bias, either pro-bike or anti-bike. I’ve tried to cut the bias and keep the question. Whatever your perspective, I hope these answers help to create harmony between cars, bikes and pedestrians. Please use this knowledge for good, not evil. Now, let’s get started. Continue reading “Bicycle Question Round-up, Part 1”

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When to Stop for a School Bus

Q: Am I required to stop for a school bus that has its red lights on to let some children off if there are two lanes in both directions and I’m going the opposite direction?

A: There are at least three good reasons to know when it’s okay to pass a school bus and when to stop. The first, and most obvious reason, is that we want kids to be safe. Young kids don’t always understand the consequences of their actions around traffic, so we have a responsibility to be extra-cautious when they’re near the road. The second reason is that illegally passing a school bus is expensive. The State Supreme Court has set the base penalty at $419. And unlike some other traffic infractions, an appeal to a compassionate judge won’t lower the fine. It’s written into the law that the fine cannot be reduced. Reason three: Other drivers will think you’re a jerk if you pass a school bus when you’re not supposed to pass. Most of us have specific traffic violations that, when we see them, we really find obnoxious, and for many people, passing school buses illegally sits near the top of that list. Continue reading “When to Stop for a School Bus”

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What’s Your Goal?

I’m not sure if this should be called a PSA or a short documentary, but it asks some great questions on this theme: What should our goal be for traffic fatalities? You’ll probably recognize some of the backgrounds; this one comes to us from the folks at the Washington Traffic Safety Commission. Instead of graphic crashes or big budget effects, this short documentary (there, I decided) lets people in our own community answer the questions. It’s about five minutes long, and I might be biased since this comes from our home state, but I think its worth all 309 seconds.