First Ever Computer Modelling of How Cyclists (And Motorists) Hit Potholes

28th December 2023

The Spokesmen Cycling Podcast

EPISODE 344: First Ever Computer Modelling of How Cyclists (And Motorists) Hit Potholes 

SPONSOR: Tern Bicycles

HOST: Carlton Reid

GUEST: Kara Laing

TOPICS: Automotive engineering analyst Kara Laing, an everyday cyclist, explains her new work on the modelling of hitting potholes.


Carlton Reid 0:13
Welcome to Episode 344 of the spokesmen cycling podcast. This show was engineered on Thursday, the 28th of December 2023.

David Bernstein 0:29
The Spokesmen cycling roundtable podcast is brought to you by Tern bicycles. The good people at Tern are committed to building bikes that are useful enough to ride every day and dependable enough to carry the people you love. In other words, they make the kind of bikes that they want to ride. Tern has e-bikes for every type of rider. Whether you’re commuting, taking your kids to school or even carrying another adult, visit That’s t e r n to learn more.

Carlton Reid 1:02
In this last episode of 2023, I talk with automotive engineering analyst Cara Lang, who explains her new work on the modelling of hitting potholes. She describes how she recently spent 600 pounds for a pothole dinged car wheel, but goes on to explain that hitting the same pothole on her bike could have cost her her life. I’m Carlton Reid. And this episode could be literally and certainly figuratively, the most impactful in the show’s 17 year history. All right, you you direct message me with the fascinating piece of research, which we will talk about, and hopefully at length, and you will very quickly discover how little science I know. Tell me first of all, because you’re an engineer, [yes, I am]. Your background. So give me your trajectory in life. Before we even get on to cycling. Just tell me how you got into engineering. And then segue into what you’re doing now.

Kara Laing 2:13
I went the long way round into engineering. I’m a mathematician by education. And when I finished I finished a PhD. And I decided I wanted to do something to make the world a little bit safer. So I decided that I was I wanted to work on car safety. Didn’t know how I was going to do this. It turns out that just at that time, about 20 something years ago, finite element modelling was becoming the next big thing in car safety. So what car companies were starting to do and is now established practice is that they would take their car design, and they would build a computer model of it. And then instead of running car crashes on actual cars, they would run it on in the computer model. The way we build the model is you take your your different parts of the vehicles and instead of being one large, complicated shape, we turn them into lots of little little pieces that we called finite elements. And it’s quite simple to work out the physics for what’s happening when you when you squash something you know how much it’s going to resist, and how much it’s going to push the next element in the chain. But you just have to do it about 2 billion times two model a car crash. I went into that. And I’ve been working on that now for 23 years coming up for 24 years. I started off working in full vehicle crash modelling. And then I started working on a company for a company my current employer Vectayn where we do a lot of what happens to people inside vehicles. So that’s my job. And I’m a technical specialist there. Really enjoy it. love talking about it can talk about it for hours. But it means that I look at the world in a way of okay, how can I look at that as a model? How can I understand what’s going on why it feels like that? Or why it looks like that or why something is reacting like

Carlton Reid 4:27
It’s a tough one to throw this on you because not not your fault. But automotive crash test things in general. Clearly focus as you were saying before about the people inside the car that’s quite natural. You want to you want to protect your customer, the person who’s physically buying that you want to protect them you’re not really that fussed about the people outside because they’re not buying your car. So do you also work on protecting people that are not inside the car? Well,

Kara Laing 4:57
this is interesting that about 2010 Euro Ncap, European new car assessment programme, started looking at what happens to pedestrians outside the vehicle. And that was the first time that that requirement had come into place. There’s now also a legal requirement for cars in Europe for an A, to some extent in the States for what happens if you interact heavily with somebody outside the vehicle, shall we say? It’s actually the sort of modelling that I really enjoyed doing. For the reasons that it’s it’s more socially supportive. I’m trying to think of the right words there. It is good for people outside the vehicle is not just a marketing thing of how safe Can you keep your family, but how well can you carry out this responsibility to the people around your vehicle,

Carlton Reid 5:52
and how well they’ve had to meet the standards. So how well do you think companies are doing?

Kara Laing 5:58
They are doing better. But fundamentally, if you will, the regulations have now changed that, or sorry, the euro in cap assessment has now changed. So that it now model vulnerable road users. So it looks at cyclists as well. It’s I think it’s it’s been significant, it’s now standard to consider that standard. Consider that in how vehicles are designed. And you can actually see that so that they are more vulnerable road user friendly. Yeah, so it’s improved, it’s still not as safe as the occupant.

Carlton Reid 6:38
Because there’s theTesla cybertruck. You know, that’s clearly never gonna pass any European regulations. It’s just it’s a death machine on wheels for people outside the vehicle. I’m sure it’s incredibly safe for people inside. But outside, that’s just a death machine. And we don’t want to see those kinds of things coming across to me, we’ve got another SUVs, so

Kara Laing 7:02
don’t get me started on SUVs. I have to be a little careful what I say, yeah, I, I was passed by a Humvee the other day, I was cycling down a single track lane, on my way home from work, and I pulled into a parking space and this thing went past me and I don’t even know if they knew I was there. It was enormous. If it had helped me, I don’t think they’d have noticed. And yet, the cyber truck, I don’t know whether there will be any publicly accessible results from testing. I’d be very interested to see how it performs. It’s a truck. So it’s quite possible it won’t even need to pass through any Europe any federal requirements. I don’t know how it’s going to be sold here.

Carlton Reid 7:54
I’ve not I think it’s really easy answer that one for a very long time. And if it changes by EOB, yes, the illustration on the Vectayn website is of a kind of like an estate car with probably quite big, wide, you know, nice crumple zones. And if you you know, you get hit by that you get thrown up, I’m assuming and then shove to one side kind of thing, whereas an SUV hits you and you just get your splattered with an SUV hitting you like getting

Kara Laing 8:21
better. But I wouldn’t want to be a six year old kid standing in front of one.

Carlton Reid 8:25
No. So you mentioned cycling from work there. So what kind of cycling apart from cycling to and from work? Is it something that you’ve always done? Why do you get into it late? We’re kind of you’re

Kara Laing 8:37
My cycling trajectory. When I was a student, I couldn’t afford the bus pass. So I bought a bike. And it turns out, I actually really enjoyed it even though that bike was so terrible that somebody burgled our shed and stepped over my bike to take all the others. Cycling is part of my happy space. It’s how I get to and from work as much as I can. It’s cheaper than the gym. I cycled for leisure whenever I get the chance. It’s something I do with I’ve got a cycling buddy. I tried to cycle with my family. But of course, it’s never enough cycling. And cycling to and from work is just my way of fitting a little bit in and getting a little bit fitter and reducing my carbon footprint. It’s a win win win win scenario for me.

Carlton Reid 9:28
So since that previous bike that the thief stepped over, you’ve invested in something nicer.

Kara Laing 9:35
Yes, yes. Yeah, I it turns out I now have a winter bike and a summer bike. Mainly so that in the winter, a lot of my route. I take country lanes because it’s quieter and it feels safer. But they’re unlit and you can’t see the potholes,

Carlton Reid 9:55
which is a great segue into yours So, you contacted me? Yes. I was writing, basically about the transport minister. You’re ignoring cyclists in this announcement about London’s roads and a bit of cash that’s going to be pumped into into road resurfacing in London and you just eat basically just and in fact, the press reserves to plan for transport press release, pretty much 99.9% of it was motorists motorists known as like, oh yen and it kind of like maybe potholes affect cyclists as well. It was just like a throwaway line right then. But then your research your research shows that is completely the opposite. Absolute. So describe. I mean, yeah, I could describe this but let you describe your graph to me, which shows this in absolute me I don’t be a scientist to realise Oh, that particular curve means that hurt compared to that particular Bob little line, which is the motorists line. Yeah, might might scratch a hubcap, they ain’t gonna die. So describe your graph. Okay,

Kara Laing 11:03
well, what I did is I went around mid I carried a tape measure around for a couple of weeks measuring everything I could I have built a computer model of five different types of wheel I’ve my first question was wider potholes hurt more when I’m riding my road bike than when I’m riding my mountain bike type bike. It’s got fatter tires, there’s a lot more air in there the rubbers thicker and so on. And then I thought but what’s it like for other road users as well? So I’ve I had a conversation with a friend where I said can I please measure the wheels on your chair, I measured my my bike I found an online model I found a paper describing the modelling of a car tire. And we’ve there’s there are a couple of open source car models out there. And I also modelled a an E scooter by finding one of those we’ve got higher scooters in the city I live in So there’s me standing there with my tape measure measuring it okay the diameter is this how have how squiddy does that feel trying to find out a little bit about the E scooter tire. And what I originally did is I dropped them all with an appropriate weight on them which is the equivalent of riding off a 50 mil curb off into a 50 mil deep pothole. I’ll go back to 50 mil in a moment. And I looked at the amount of debris that the person or the top of the shock tower for the car would experience from dropping into that pothole. And basically a car experiences about a third of the amount of acceleration that a road bike does so it explains why when I when I drop into a pothole it hurts I’ve since run the what happens when you ride out of the pothole. And it’s even more stock that cars are designed to drive over curbs and bikes, scooters and wheelchairs really aren’t that the amount of force that somebody riding a bike has to be able to control with their hands is we’re talking about 300 somebody’s giving you 300 kilogrammes to hold suddenly and yeah and that explains why it’s quite difficult to ride into an outdoor pothole

Carlton Reid 13:48
you mentioned shock tower before Yeah. That’s on the car that I mean I’m assuming that says the suspension system is that your definition of a shock tower

Kara Laing 13:56
Yeah, the top of the suspension system I think I sent you some images I’ve taken as little as I can of the car model because my my work of happy to let me do this but I need to kind of sneak it through when we’re not running big crash models of something else.

Carlton Reid 14:16
I do recommend people I’m gonna I’m gonna post this high res version of the graph that you did posted on Twitter when you sent me this this high res version I will post that on on the show website so people can go and scare themselves silly basically by looking at this and and probably it will go semi viral in that when anybody comes and says oh look my you know my car was you know hubcap was dented by this this pothole, just show this graph. Yeah, but look what it happens, you know, with cyclists die, they don’t and they go into your, your, your, your modelling here. So the shock tower, we we’ve kind of got that definition. So the MTB, the mountain bike, one that again that was that’s a suspended product. You’re talking About a suspended mountain bike bike with front suspension or what

Kara Laing 15:04
I just took that That one’s nice and simple. I just took it from the middle of the wheel. I didn’t I didn’t have any model for a mountain bike suspension. So I took so there would be a little bit of extra give in the system. Yeah, so mountain bike is is an optimist is sorry, is a pessimistic curve, and suspend it shows how suspension would help. But this brings me back to to one of my initial questions when I cycling along and I thought I wonder about that. The next lunchtime i I logged on to my institutions library and started looking for information about what people had already done looking at the amount of the amount of force that is experienced through a cycle, hitting an obstacle or dropping into a pothole. And there was nothing. Nobody has done this work as far as I can find. I haven’t spent hours and hours going through the literature search but there really isn’t anything out there. And that’s quite shocking. It’s I’m also going to bring it back if I may Colton to the 50 mil. I chose 50 mil most councils in the country assess their potholes by they’ve they’ve moved over to a risk based assessment of potholes. And they it has to be 40 mil deep and however big it needs to be the county I live in. They don’t count unless they’re 50 mil deep

Carlton Reid 16:41
as the No there’s no government regulators. It has to be this deep. This is a each council does each different. Oh, okay. Yeah.

Kara Laing 16:47
So in? Well, I’m in Essex, and in Essex unless it is big enough for a car wheel to fall into. And unless it is at least 50 mil deep. It doesn’t count as a risk. So I actually I sent the initial graphs that I sent to you initially sent to my counsel, I’ve never heard anything back.

Carlton Reid 17:11
Yeah, cuz there’s all this like, Well, yeah, of course that’s gonna hurt a cyclist. What’s the way you tell us something we didn’t know. I mean, that’s that’s part of, you know, the kind of the cynical thing here is like, well, of course. Yeah. But, but that isn’t how the Ministry of Transport press release. showed it at all. It really was. This is hurting motorists. Yeah, it was like in Cyprus, just we’re just not in the equation here. But at this point, Kira was called away. So that’s a great spot to cut away to my colleague, David for a quick ad break.

David Bernstein 17:45
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Carlton Reid 18:45
Thanks, David. And we are back with Kara Laing and her work on the computer modelling of dropping into potholes. So your work all right with with with this, this is a very graphic thing that you could show the powers that be and that’s something that’s like quite physical compared to you know, here is this cyclist who died from this which you would think would actually be more powerful in many respects, but often isn’t. Whereas this is something that anybody can look at and go oh, yeah, we need to fix those potholes. Because look at that, but what cyclists when they when they when they sadly die from hitting potholes. It generally isn’t the pothole that’s killed them it’s generally I’d have to again do a literature research on this and find out exactly but it tends to be hit pothole you know, wobble and then fall into moving motor traffic that’s falling behind that aren’t breaking quickly and and they get squished unfortunately from that what’s happening base that 300 gramme await you suddenly got that makes you wobbles you’re not you’re not gonna die from the there’s no other vehicles around you’re probably okay it’s the other vehicles are Round that’s gonna kill you.

Kara Laing 20:01
Yeah, I cycling off a pothole like that I don’t think I’ve got the strength or the reactions to control it, I don’t have the skill to control it. It would be that is the kind of thing that would take somebody off their bike. We also have potholes around here that because they are wedge shaped, you can find yourself with a wheel completely trapped and no way of getting out of it. So yeah, that are a real risk for cyclists in a way. In a car. It’s uncomfortable. I mean, I recently had to pay 600 quid for a new wheel after a pothole on a country lane. But I’d far rather be paying 600 pound and having bits of me put back together or be paying or having my family paid for my funeral.

Carlton Reid 20:51
Yes, yes, that again, that is the reality behind your your graph, Bear. So tell me that the practical applications of your graph, what could activists do with your graph? What could you do with that graph?

Kara Laing 21:05
I had do some more on this on my to do list. Since this was work that I did during furlough, I sort of had to do more with this. One of the questions that somebody asked on your Twitter thread is what is the difference between a 50 mil curve and a 40 mil curve? And my plan is to run that and find out that to quantify what the increase in I’m not going to say perception what the increases of experience, because I think that minimising that acceleration pulse that is felt through the arms through the bike through the wheelchair, that’s got to be a good thing. It needs to be reduced. So that I mean, if we say if councils are saying that a car that a pothole needs to be repaired, when a car experiences that kind of Jolt, then we need to reduce the standard so that when a cyclist or a wheelchair user or a scooter user experiences that kind of Jolt, how do we need to change the requirements so that the risk level is the same for all road users? So

Carlton Reid 22:17
how do you do say effective dropping into a 10 Min millimetre pothole 20 3040 5060 isn’t going up. And then you did plot that out? As look, if it’s this level, this is what’s going to happen. So you really ought to be doing potholed at, say 30 millimetres? Is that what you can do with your, your research, you can actually plot all these things out and think, look, if it hits this depth, you got to do something about it? I think

Kara Laing 22:42
so. But what I am aware is that, for example, my estimate of the E scooter wheel is wrong. I know it’s wrong. When you look at the animations, it’s a bit squishy. It just doesn’t look right. So I would welcome any input from anybody who’s ever stuck an accelerometer on their bike and gone through a pothole, to find out what actually happens in the real world. This is, from my point of view, an initial model. And it’s as good as I can make with the data I’ve got. But I don’t have all the data I would like.

Carlton Reid 23:17
See, there’s two answers to that. That was the two things can pop pop in my mind. The last show, in fact, with Mr. And Mrs. McAleese, who have now moved to Australia, their tech, which is the you know, the See.Sense lights, well, that has an accelerometer, and that does track events, you know, pothole events. And then, you know, plot on maps when it’s linked to a link to the iPhone when when you can opt in, basically to, to, so the data is shared, anonymized but shared. So potentially See.Sense would have some of that data. So I’ll put you in touch with with them because I’m, I’m sure I’m sure they would love it right. Please do. Like it’s sort of a joke here, but also real right up the street. This, this kind of modelling will be to them, put it that way. But also just iPhones and and Google Pixel phone and smartphones, gentlemen, they do have accelerometers. So presumably you could get an app could be created to measure this either. In the CCENT terms, it’s like it’s just happening all the time. You just fit the light and you just you forget it, or you could genuinely go over. You know, a stunt stunt doubles could go over potholes and see if your graph is the real world. Yes,

Kara Laing 24:45
absolutely. We, we we just compare information. I mean, I’ve got a model of, of different sizes of wheels. I can make more models. I’d love to see it I’d also be really interested to see to understand from Wheelchair users point of view, how it affects them? Because I’ve modelled what happens at the wheel? But how does that affect the wheelchair user?

Carlton Reid 25:10
So this the model that you’ve got here, have you hit the lip of the pothole, then you go down into the pothole as a wheelchair user scooter user cycle user, you’re probably going to hardly notice it in a car. We’ve all kind of we’ve kind of established that. But then what you said before was, it’s actually coming out. That is potentially and that’s the work you’re still doing or you need to do more work on. It’s the coming out. That is potentially the worst bit. Yeah,

Kara Laing 25:37
it appears to be where I’m getting much more sharp pulses. They’re called pulses, the curves, I’m getting much sharper pulses. And the the issue is, it appears to be that the rubber does everything it can but if the pothole is too deep, then the rim of the metal hits the rim of the wheel and then hits the structure. And on a car tire because you have got 100 200 mil of space before you risk bottoming out that’s why it’s not anywhere near as much an issue on a car as it is on a road bike wheels are really thin, it makes

Carlton Reid 26:18
sort of sense that it is going to hurt hitting the second lip. Because the first lip is you’re dropping it down you can imagine your your tire and perhaps any suspension you’ve got will maybe cope with that. But if you’re then travelling when some of these potholes are pretty big, and you might travel perhaps half a metre or metre before you hit the lip but it is that second bit where you’ve got to be very careful of what’s happening coming out. So just that appreciation alone can be like a lifesaver.

Kara Laing 26:52
Yes, absolutely. And also what if you don’t hit the edge the the exiting edge straight? What if you hit it one key How can you I haven’t modelled that but I can it’s something that we can the models can become as complicated as we want them. How much strength do you need in your arms to be able to control that Yank of the wheel

Carlton Reid 27:16
here in Northumberland I’m gonna have you said this bad message in Northumberland we have cavernas almost literally caverns you down and hardly be seen by anybody Yeah, they’re pretty deep so Northumberland is notoriously bad for potholes and I’m maybe Essex is is the same but councils need to be shamed I know there’s Cyclists’ Touring Club as of bold you know we asked cycling cycling UK of today they were pretty big on potholes previously and I’ve been looking just recently when I’m when we’re doing this as an all women’s their pothole stuff and they haven’t done anything for a while but haven’t really resurrected their campaign they had an app you know fill that pothole, they had all this sort of like campaigning materials built around potholes, and the prevention of and the filling in of and they seem to have died away again. Hopefully this research can actually help them with statistics and with with graphs, literally with graphs, actually resurrect that campaign. So councils, Northumberland, Essex, wherever you live, can be shamed into filling these things in

Kara Laing 28:31
that will be wonderful. And I’m happy to talk to anybody. I mean, fundamentally, my issue is I dislike potholes as a cyclist. And I’d like them to all go away please. Anything I can do to encourage appropriate repair of potholes with round the corner from me. They’ve recently filled a load of potholes in that our wheel size, but then they’ve chosen not to fill in the ones that are cycled tire size around the corner. Anything that encourages a wider acceptance of who road uses quite might be.

Carlton Reid 29:11
And that’s good for putting the wheelchair in as well. Is that like a standard wheelchair with solid tires? Is that what kind of wheelchair was that? Or is that like a road cycling type wheelchair?

Kara Laing 29:26
This was can I find any wheelchair tires online to get any dimensions out of them? It’s an airfield we’ll talk airfield tire I’d quite like to do a rubber one but I’ve not been in not being in this position to take somebody’s wheelchair well apart and have a look at what it’s made off. Because

Carlton Reid 29:46
that thing literally saves us in that the air do pneumatics in a tire literally saves us it doesn’t just make more comfortable we can hopefully hit a pothole and survive as long as we don’t hit that wobble and then get hit from behind. Yes Speaking

Kara Laing 30:00
at speaking as an engineer, this has actually been really interesting looking at how the tire works, looking at how it stretches and how it boulders and how it recovers to carry on doing its normal job of just going round.

Carlton Reid 30:13
So you’re using … Vectayn is allowing you to use their finite element modelling computers to do this. But is this your Is this a spare time thing? So this is like a lunch break or something? And they’re not expecting you to guess, come up with anything practical for their business? Or, oh, might you be able to?

Kara Laing 30:33
I think, I think there is plenty of scope here. Unfortunately, I can’t afford to become a customer of my own company. So if anyone is out there and wants, once the modelling done, the groundwork is already there, it would be really affordable. And I’d love to do it for you. At present, it isn’t. We don’t have a client for this. If anyone if anybody is interested in this, if any councils are interested in this in a more well defined assessment of what risk based pothole repairs should look like. I’m, I’m definitely you’re definitely the analyst you need to talk to. We’re

Carlton Reid 31:16
on that note correct. And it has been fascinating. And as you said before, you could talk for hours about your day job. Or we could talk for hours about deformation of tires going into into potholes. But we can’t speak for hours and hours and hours. So we got to stop at some point. So this is a perfect juncture, I guess to say, who you are and how people can contact you. Okay,

Kara Laing 31:38
well, the best. The most detail on this is on my LinkedIn profile. My name is pretty there’s not many of us. It’s pretty obvious who I am. If you look for me,

Carlton Reid 31:49
and the Laing is L A I N G Yes.

Unknown Speaker 31:54
And it’s Kara with a K.

Carlton Reid 31:57
It’s been fascinating talk to you. I’m going to go away and I’m going to try and link you up with interested parties here. Season please. Cycling UK, they should be doing something on this because it’s absolutely essential work. You’re doing that and it’s working I didn’t even know hadn’t been done. So that’s, that’s pretty scary.

Kara Laing 32:18
Exactly. Exactly. That’s what shocked me most about this. Fundamentally, really selfishly, I’d like to get this published somehow in some format in a journal would be great, but in a magazine would be great. And then I can put it in front of my council and say, Look, you’re 50 mil assessment for curb decks. For for pothole that is inadequate, you need to reduce it, or you need to think about where you apply that and make it genuinely risk based and not just motor normativity risk based.

Carlton Reid 32:53
Thanks to Kara Laing there and thanks to you for listening to episode 344 of the Spokesmen podcast, brought to you in association with Tern Bicycles. Show notes and more can be found at The next episode will be out next year — dad joke there — but meanwhile get out there and ride.

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