Curious Conversations, a Research Podcast

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Travis

When it comes to cycling, my knowledge pretty much begins and ends at I do know how to ride a bike. So, in terms of what makes this a safe activity, both from a behavior and an infrastructure standpoint, I really don't have that many insights. But thankfully, Virginia Tech's Laura Hamm has a ton of insights in this very area and was kind enough to join the podcast to teach me all about them.

Laura is a senior research associate in the division of vehicle driver and system safety at the Virginia Tech Transportation Institute. research focuses on the safety and mobility of vulnerable road users, including cyclists and pedestrians. So Laura helped me understand the landscape of cycling in the United States right now, how many people are riding, and why don't more people ride? It turns out that safety is a primary deterrent for a lot of people from riding. And Laura explained why getting some of that safety information, specifically about bicycle and vehicle collisions, is actually really challenging. She shared a project that she's currently leading that's hoping to use naturalistic data from cyclists to help bridge that knowledge gap and also shared a project that she's working on with the Virginia Department of Transportation uses traffic stress as a measure to help gauge how safe or unsafe roadways might be for both cyclists and pedestrians.

So if you like I am interesting bridging your own knowledge gap when it comes to cycling and cycling safety, think this podcast will have a lot to offer you.

I'm Travis Williams and this is Virginia Tech's Curious Conversations.

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Travis

Well, I wanna talk to you about cycling safety. And I thought maybe a good place to start that conversation is, was to simply maybe kind of lay out the landscape of what cycling looks like. I'm curious, are people doing it more than they used to? And I guess when it comes to safety, are we seeing an increase in collisions, safety hazards, however we would like to phrase it, however we should phrase that. ⁓

Laura

Yeah, so when you think about the landscape of cycling, it's going to be very location dependent, right? So let's assume we're talking about the US here because that's currently my research focus. But across the US, you have really drastically differing rates of cycling as transportation, depending on where you live. So we do have in major urban centers, pretty high rates of cycling commuting, at least for the United States. So when you look at like Boston or New York City, get high rates of active transportation, people walking and commuting to work on bicycle. But across most of our country, cycling, the use of cycling as a form of transportation is very low. I think the average nationwide is less than 1%. So across the country, less than 1 % are using bicycles as their primary form of transportation related to the safety question. So when you ask people, you know, why don't you cycle for transportation? The number one answer is I don't feel safe doing it. And when you look at the statistics, they back that up. So we've seen an increase in cycling fatalities from I think around 2015 until the latest year we have data, 2024. So they've increased in both number and in the percentage of total traffic fatalities nationwide and you know, it's a huge problem. would, I would describe it as a crisis. had, you know, when you include pedestrians, had, think over 7,000 pedestrians killed in traffic collisions last year. and cyclists think is around over a thousand. and there's some evidence to suggest that, that the latest year data will show a decrease, which will be great, but it's still much, much higher than we want to see and much, much higher than other countries where you have higher cycling mode share. In terms of are more people doing it, think it is increasing mostly because the proliferation of electric devices. So e-bikes have been a great tool in getting people who might not have considered cycling as a form of transportation to try it out. But at the same time, that means you're having more novice riders on the road and maybe people who are less comfortable riding around vehicles, which is gonna create some inherent safety issues. And so what we're seeing is an increase in interest in bicycling and particularly e-biking, but at the same time, a lack of infrastructure that's appropriate for making cycling safe and comfortable for those who want to do it.

Travis

I'm guessing when it comes to, collisions, do we know what some of the most common factors are in causing some of the collisions and problems that cyclists have?

Laura

That's a great question because it gets at the core of what I'm interested in and what I'm trying to figure out. So when you think about a crash between a vehicle and a bicycle, there could be tons of contributing factors, right? And we have a very well-established system for looking at motor vehicle, motor vehicle crashes. So when two cars collide and there's a crash, there's a very defined scenario in terms of what the police do, what data they record, what happens after the crash, and how that data is incorporated into larger data sets that then we can analyze afterwards, try to better understand what's going on, what areas are dangerous, what infrastructure do we need to change, what laws do we need to change, that sort of thing. But this system, it kind of breaks down when you're looking at vehicle crashes with cyclists. And that happens for several reasons. I think the primary one is that a lot of crashes between vehicles and cyclists don't get reported. So unless you have a severe injury, so the cyclist is taken to the hospital, you're oftentimes not going to get a police report. The police may never even be called. So I think we're missing out, don't have a magnitude of it. The studies that I've seen would suggest that it's probably at least 30 % of crashes aren't being recorded at all. And then when you do record the crash, the data that you're getting out of it is oftentimes incomplete and also inaccurate. So one issue we've seen looking at epidemiological studies, when you try to compare the hospital records of say an injured cyclist to a police report, If you can match them at all and oftentimes you can't, they don't agree. So the injuries you see from the cyclist in the hospital are not reported on the police report. And then there's the question of trying to reconstruct what happened, which would let us understand contributing factors. And that's often very, you don't get a lot of data from the police report when there is one filed. And that's because we don't have a great system of like helping the officials that are responsible for collecting this information, helping them understand what is relevant. I think, you know, most people in this country drive a car. They're familiar with driving a car. So when they're trying to understand what happened in a car crash, they know what is a contributing factor. What is something that would have led to this crash? That's just not the case with bicycles. Most people recording this information probably don't ride a bike. They probably don't understand how a bicycle might interact with vehicles in traffic. And so asking them to identify contributing factors is probably not reasonable. And then there's the problem of, you if you think about the scenario where a cyclist gets hit by a car, EMS will arrive if they're injured and need to go to the hospital, and EMS will often get there before the police officer that's going to file a report. So the only account of what happened is coming from the motor vehicle driver. And for reasons you can imagine, like the driver has some motivation to report a story that is favorable for them not being found at fault. So we're not getting accurate information about factors contributing to cyclist crashes.

Travis

yeah, it sounds like a really challenging area to even get enough data to, to make decisions about. I think one of the things that you are piloting is a naturalistic driving study that might help us better get some of this data. I'm not sure how far you are along in that, but what can you tell us about maybe some of the things that you hope to gain from that study.

Laura

Yeah, we have, or just wrapping up a pilot naturalistic cycling study. So what that means is that we take a suite of instrumentation like cameras, inertial measurement, know, that let's look at how cyclists are accelerating, decelerating.

We have a radar unit so that can detect approaching vehicles and let us understand how fast vehicles are approaching cyclists and passing cyclists. We have a LIDAR unit, so what that does is let us pick up objects in the vicinity of the cyclists. We've primarily used it so far for looking at how close vehicles are getting to bicycles in different situations. So we can combine that LIDAR and radar data to look at passing vehicles and see how close are they and how fast are they going. And we're interested in that because vehicles overtaking cyclists is one of the primary fatality mechanisms that we see. So that makes up, I think most, that's the most common fatality scenario for a cyclist is when a vehicle, so passing. So yeah, vehicle approaches the bicycle from behind and goes around.

Travis

What does that mean over overtaking?

Laura

So yeah, cyclists getting hit from behind is one of the most critical scenarios in which cyclists are dying on our roads. Yeah, so we've done this pilot study where we instrumented five participant bikes in Blacksburg and collected data for about four months. And like I said, it's a pilot study. So the idea was kind of to test the system, make sure that it...worked properly on participant bicycles, so wasn't interfering with how they're riding. And it's just collecting data as they go about their day-to-day business as they normally would. And then we've started some preliminary data analyses just to make sure that we're getting the kind of data we want to be able to look into the safety issue in more detail. So the long-term goal is that we would kind of develop this larger naturalistic cycling data set that shows us both, you know, how people are riding in normal conditions. So just like a safe day-to-day ride, what does that look like? What are the acceleration and deceleration profiles look like? And then we can start to understand, well, what do unsafe events look like? What do uncomfortable situations look like from a cyclist perspective? And where do those things occur? And once we can do that, I think we can get a lot of really interesting information into not crashes, obviously we don't want to see a bunch of crashes in the data, but VTTi is kind of the pioneer in naturalistic studies when it comes to motor vehicles. And what we're able to do with motor vehicles is develop this like sweep of triggers or thresholds in the data that are indicative of dangerous events. And those happen so much more frequently than crashes, which makes it valuable because you have a much larger data set of events that may be indicative of a crash. So almost a crash. And then you can start to look at, what are the contributing factors there? Is it infrastructure? Is it how cyclists are riding? Is it how drivers are behaving in certain situations?

Travis

Yeah, I'm glad you mentioned that because I was going to say for people that maybe listening to this and don't know VTTI is home to, believe, like the largest pile of naturalistic driving data, just stuff they've collected from people.

Laura

Yeah, I like the idea of it being a pile. ⁓

Travis

Pile may not be the word that they would like to describe it, but I think at one point, and I forget the exact number, but it would take years and years and years for you to watch all of it. It's, it's that much. and so there's a lot of value there. So the idea that, that you're going to try to start to amass the same type of data with cycling, I think is fascinating. you, you mentioned infrastructure a little bit and some of the other projects that I've heard you're connected to is this work with the Virginia department of transportation to help create some sort of mapping of maybe safer and non-safe locations that people could cycle. Maybe a better way to say this, maybe a map that would help me as a cyclist navigate where I shouldn't be riding or maybe some of the safe factors there.

Laura

Yeah, that could be one use of the map. So I'll start from beginning. So what I'm doing is using a well-established method that was developed in the United States to kind of gauge the stress level of a certain roadway to ride on as a cyclist. It's called level of traffic stress. And what it does is you pull in various attributes of a certain roadway segment. So How many lanes are there? What's the speed limit? So generally how fast are vehicles going? What's the traffic volume? So is it constantly seeing motor vehicle traffic or is it like a quiet residential road where you don't get a whole lot of cars driving on it per hour? And then what kind of bicycle infrastructure does it have? know, is it just a two lane road for cars or is there some sort of bicycle facility like a painted bike lane or a protected bike lane or a separated path. So you take all those attributes of a certain roadway and look at them together and try to estimate, you know, would this be good to cycle on? And there's lots of methods for doing this. You can use, you know, anything from a few easily available metrics to, you know, hundreds of very specific, you know, lane widths, bicycle lane widths. Are there parked cars? You can get as detailed with this as you want, but what we're trying to do at VTTi is help VDOT implement this sort of mapping at a network level to understand where there's gaps in connectivity and accessibility in the network. So one of the things that's hard with bicycle infrastructure in particular is that, you know, as a country, as a whole, like we tend to not have a whole lot of it at this point in time.

And where we do have it, it's not necessarily connected. So maybe you have a bike lane on a certain street, but then it ends and then you have to jump in with motor vehicle traffic. And at the same time, we have really pretty restricted budgets for developing new infrastructure. So when you look at the transportation budget as a whole, think active transportation, it depends on where you live, but it generally gets anywhere from 0.5 % to 5%. of the funding. So what we find is that localities are facing difficult decisions when it comes to, okay, we have this much money to implement some improvements for bicycle safety, but we have a huge network and we can't put bike lanes everywhere. Like how do we decide where we want to focus our resources? So the idea with this level of traffic stress mapping is that you can present a network level map of the existing low stress connections. And then identify where are the gaps? Where are the gaps in this network that are preventing people from getting where they live or where they are to where they want to go? So there's kind of two components to this project. The first is that we're trying to look at what's the best way we can help practitioners implement level of stress without using too much detailed data and without having to have too much expertise because we want them to focus on getting these projects done, not doing extensive data collections and mapping. And one thing we're able to implement, which I think is unique at VTTI is this issue of vehicle speeds. Like I mentioned, level of traffic stress is typically based on speed limit. But we have a lot of actual speed data from telematic systems, from vehicles, throughout the state of Virginia. And what we see is that, this is probably won't come as a surprise, but speed limit isn't a great predictor of vehicle speed in a lot of cases. So what we've tried to do with data that's already available is update these level of traffic stress predictions based on how fast vehicles are actually traveling versus how fast the speed limit sign says they should travel. And I think that's resulted in some improvements, at least in the test case we've done in Blacksburg of more accurately predicting how stressful a road is to ride on. So that's the first step. The second is really looking at accessibility. So bike infrastructure is great, and there's some really good research that's come out of the University of New Mexico. it shows that when you build new bike infrastructure, people will actually ride it. If you build it, they will come. It seems obvious, but it's No one's actually documented it through a proper study until recently. then beyond that, when you build an isolated piece of bike infrastructure, it doesn't get as much increase in ridership as when you build a connected network. And that seems obvious too. But this idea of connectivity and accessibility is really important here. So we're also in addition to providing this kind of mapping of stress levels, We're trying to provide mappings of accessibility. So looking at where do people live in Blacksburg and where are the employment centers? And if we try to connect them at low stress bicycle routes, is it possible one, and how much longer is it going to take than if you just did the most direct route? So, you know, for example, if you're trying to get from downtown Blacksburg to let's say like Corning on 460 Business, like the fastest way would be to ride 460 Business, but that's obviously not gonna be the lowest stress route. So we would say, is there a low stress route available? And if so, what's the detour penalty in terms of distance that you have to ride extra and how much extra time it's gonna take.

Travis

All that that sounds fascinating. It sounds like a lot more goes into it than just infrastructure I'm curious if you all were you all watching me drive around speed limits on is that how you got that data like

Laura

I don't think we de-identify all the data, so you won't be able to tell.

Travis

Okay. Well, that's, that's really good.

Well, that is all, that is all fascinating. It sounds like it'll be a super helpful tool because I think everything you said, even, even though I'm not an avid cyclist, but everything you said to me even relates to me as just a person that runs and walks places as if I can walk to a place, I'm, you if I could walk from where I live to the library in a place that didn't make me cross some very busy intersections and stuff, I'd be more likely to do it.

Laura

Yeah. So that like, that sentiment is, that seems obvious, too. But it's also something that's kind of new in the literature. So there was a study that just came out of Arizona State, and they surveyed people across the country and said, you know, if it were possible, if it were safe, you know, would you be interested in living like a car free or a car light lifestyle? Like essentially what you said, like if you could walk to the library and you didn't have to do Frogger across a four lane road. Like, would you want to do that? And yeah, overwhelmingly, a lot of people said, yes, I'd be interested. But we, you in this country, we've kind of forced people into a lifestyle where you have to drive everywhere. And so what I want my research to do fundamentally is, you know, provide the data we need to make it safe for people to choose walking, biking, transit, to choose those options if they want to. And then, you know, driving becomes not obligatory to participate in society, you know, to go to work, but it's just an option. yeah, in my ideal world, you could wake up and say, am I going to drive today? Am I going to walk? Am I going to take the bus? Those would all be available to people to get.

Travis

Yeah, that sounds great to me. I'm curious when it comes to looking at just riding environments in general, what are some things that make an environment more safe than not for a rider? And specifically maybe somebody like myself that doesn't come from like a high level of cycling knowledge or experience.

Laura

Mm-mm. that's a great question. And I should add that when we do these level of stress ratings, the goal, the lowest stress rating, which you would want to have the most of is, can a child ride it? Would you feel comfortable if your child wanted to use this road or this path? But I think it's a simple question that has a very complicated answer, right? Because there's so many factors that go into safety. When you look at the places where it's safest to ride a bicycle, they also have the most people riding a bicycle because there's this kind of cyclical effect where, like I said, when you ask people, why don't you cycle? The main reason they give is they don't feel safe. In this country, it's largely because we don't have appropriate infrastructure and mean, the easiest way to keep a cyclist safe is by physically separating them from moving motor vehicles. And when you do have cyclists mixing with motor vehicle traffic, that traffic should be going at low speed, so less than 20 miles per hour. So we need to develop like connected networks of infrastructure that let people ride separated from traffic when appropriate and when mixed in with traffic in low speed, speed calmed environments.

And once you start to do that and you get the subsequent increases in ridership, you get these kind of reinforcing safety effects. So you get more cyclists, right? And that's going to make drivers more comfortable around cyclists, more used to seeing cyclists. And that further improves safety and that further increases ridership. And eventually you get to this like safety in numbers effect where you just have so many cyclists around that it becomes, you know, a normal part of day-to-day transportation. Cars expect to see you when you do have areas of mixing, but in general, I think it really starts with infrastructure. We need basic facilities. think there is a period of time where, you know, bicycle infrastructure simply meant painting a line on a road and calling it a bike lane. What we're seeing now is that that is not sufficient for protecting cyclists. Frequently because when you install those lanes on high speed roads, you get high speed motor vehicles mixing with low speed bicyclists. And that's, that's never good for safety. So what we need is physical separation. So the use of separated bike paths or some sort of bollards, curves, things that provide like a physical separation between cyclists and motor vehicles. You know, we also face kind of cultural problems when it comes to safety, just to turn, and this is another thing where the more cyclists you get, the safer it becomes. We're in a place where, like I said, in most regions we have very low use of bicycles as a form of transportation. And as a result, think in a lot of places bicycles aren't seen as a valid road user, even though legally they're allowed to be there. I think they're commonly perceived as more of a nuisance or something you have to get around. So I think as those perceptions change and as we get cyclists out of the road because we have better infrastructure, things will get more comfortable and then safer forever.

Travis

Yeah, it almost sounds like the more riders that you have, then inherently there's some things that happen that make it more safe for all the riders. But I can just think anecdotally, I feel like it makes a difference. You know, as the number of riders go up, you may know someone who rides a lot and that probably changes how you perceive when you see other cyclists out. Cause you're like, that could be, that could be my buddy. You know, I want to be careful. So.

Well, I'm curious, maybe in the spirit of kind of anecdotal information. I assume that you're a cyclist. It would be almost strange if you weren't at this point. What's some...

Laura

I think that you can find cycling researchers who aren't cyclists, but yes, I do ride a bicycle. ⁓

Travis

That's true. That's probably just me. I'm curious, what is something from your research as you've gotten into learning about this more and finding more data, how has it influenced the way you ride your bicycle?

Laura

You know, I don't know that's influenced how I ride my bicycle, but it's certainly influenced what I'm thinking about when I'm riding my bicycle. So going back to these level of traffic stress ratings, they were kind of developed around how comfortable it would be for people with different experience levels and capability levels to ride on a given roadway. So like I said, the lowest stress, like you want that to be comfortable for children.

I've been riding my bike as my pretty much only form of transportation for, I don't know, 15 years now. And so I'm very comfortable in most situations. I'm comfortable mixing in with traffic, even though I know it's not ideal for safety or comfort. But now when I'm riding anywhere on the road, I start to think, well, how would someone who's brand new at riding a bike feel in this situation? How would someone who is elderly or disabled feel if they were riding a bike in this situation? And how can we make it so that they would be willing to do that? You you're always going to have varying levels of comfort and risk tolerance across the population, right? And our goal is to provide the facilities and provide the system, like the entire environment that makes cycling possible for everyone who wants to do it. So now every time I see an intersection, I think, you know, who, how would someone who, who is really uncomfortable around high speed traffic or noise or exhaust fumes, like how are they going to navigate this environment? Like what kind of infrastructure do we need here to make it possible for them to do so?

Travis

Yeah, that is fascinating. And that's a really cool, in a way, that that's where your research has kind of led your own experiences to go. I hope that you're able to maybe kind of shut off the work brain sometimes, not be overrun. I had this conversation with a guy that studies a lot of pollutants in the ocean and in waves and stuff. And I was like, well, can you even go to the beach anymore? Or are you just constantly thinking about it? He's like, well, you I still like it. But you I am kind of thinking about

Laura

I have to point out that cycling in general, both recreationally as a form of transportation, is an incredibly joyful way to move about the world. even if I have what you call work brain while I'm cycling, it's a very pleasant experience. This is borne out actually when you survey commuters who get to point A to point B in different ways. Cyclists are the happiest.

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Travis

And thanks to Laura for helping us better understand the factors related to cycling safety. If you or someone you know would make for a great curious conversation, email me at traviskw at vt.edu. I'm Travis Williams and this has been Virginia Tech's Curious Conversations.

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