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Revolution Requires Evolution: We Need New Roadside Safety Standards for Electric Vehicles · Thinking Transportation: Engaging Conversations about Transportation Innovations

• 0:14
  Greg Winfree (Guest Host): Hey everyone. Welcome to Thinking Transportation--conversations about how we get ourselves and the stuff we need from one place to another. I'm Greg Winfree, agency director of the Texas A&M Transportation Institute, and I'll be your guest host for this episode of Thinking Transportation. A bit fewer than 1 percent of total vehicle registrations in Texas are electric vehicles, but almost 7 percent of new vehicles sold in Texas last year were EVs. So the number of EVs on Texas roads will continue to grow over time. Ensuring that these EVs operate safely and collaboratively with other road users will be a function of how well our roadside safety standards match up with these new types of vehicles. Today, I'll be talking about that with Dr. Roger Bligh, TTI's senior research engineer and Roadside Safety Program Manager. Roger has a PhD in civil engineering, is a licensed Professional Engineer, and was named a Regents Fellow by The Texas A&M University System Board of Regents in 2010. Roger, thanks for joining me.
• 1:23
  Roger Bligh: Hi, Greg. It's a pleasure to be with you today. I always enjoy opportunities to discuss our research program and roadside safety.
• 1:31
  Greg Winfree (Guest Host): That's awesome. And I believe our listeners are really gonna be energized about hearing this conversation. So why don't we start out by level setting . You know, it seems obvious from the name, but what exactly does TTI's Roadside Safety Program focus on?
• 1:47
  Roger Bligh: So when we use the term roadside safety hardware, that generally refers to any device that is intended to help reduce the severity of a roadside crash. So we're talking about devices such as guardrail or median barrier, like concrete barrier or cable barrier, bridge rails, crash cushions, all those types of devices. And our program designs tests and evaluates those devices to help improve the safety of motorists should they happen to depart the roadway.
• 2:20
  Greg Winfree (Guest Host): Okay. I know folks are familiar with guardrails and cable-medium barriers. They're the kind of equipment that are on roadways across the country, but they never really focus on those. So let's talk about the safety standards. How are the safety standards set for guardrails and barriers?
• 2:37
  Roger Bligh: Well, the testing standard itself is an AASHTO document, the American Association of State Highway and Transportation Officials, and it's called MASH--Manual for Assessing Safety Hardware. So it's that document that recommends the testing and evaluation criteria for barriers or other types of roadside safety hardware. And the impact conditions in that standard are developed from real-world crash data. So we periodically review that data and develop real-world distributions, and we use that data to understand how we should be testing our devices, what speeds and angles we should be using. And in terms of the vehicles, we also periodically review sales data to determine what types of vehicles we should be using for testing.
• 3:24
  Greg Winfree (Guest Host): Well, MASH is obviously a pivotal document in this space, but do states have the authority to develop their own safety standards? Or is this a federal responsibility, or is it a combination of experts in these areas dictating what goes on our roadways?
• 3:40
  Roger Bligh: Yes. Well, the Federal Highway Administration has adopted the use of MASH on the National Highway System. And so the states will develop their standards for use on the National Highway System following the MASH criteria. So they develop their own standards and can adopt hardware from each other as desired to meet the specific needs that might exist on their highway network.
• 4:05
  Greg Winfree (Guest Host): And how can state DOTs be sure that manufacturers of roadside safety hardware have products that meet the standards ?
• 4:14
  Roger Bligh: Well, this MASH standard that we've been talking about is a performance standard. So the roadside safety devices that are being developed are actually physically tested to these prescribed test matrices to help ensure that they're performing in a certain way and will provide the level of safety for motorists that's desired. So, for example, if we were using a barrier, it's expected that that barrier will contain and redirect an impacting vehicle within the test conditions. And what I mean by that is that the vehicle should not go through or over or under the barrier. So the objective is to keep a motorist from striking an object or encountering some non-reversible terrain on the roadside. And the barrier is going to be recommended when the severity of impacting the barrier is less than what it would be if you were striking that roadside obstacle.
• 5:09
  Greg Winfree (Guest Host): Understood . Well, as you know, when visitors come to the TTI facilities here on the RELLIS Campus, the first thing they ask to see is a crash test. Now, you and your team are some of the most popular folks here at TTI. How long have you personally been involved with crash testing and how long has TTI been conducting crash-test research over the years?
• 5:30
  Roger Bligh: Well, it's hard to believe it's been this long, but , I've been designing and testing roadside safety devices for 38 years now, and TTI has been performing crash tests of roadside hardware since the 1960s. It's always a pleasure to host visitors for a crash test and talk to them about our safety research and our program because you know, roadway departure crashes, they're the leading cause of crash fatalities in the U. S., representing over 50 percent of our roadway fatalities. So it's a really significant problem we're trying to address, and I think the more information we get out about that, the better.
• 6:08
  Greg Winfree (Guest Host): Absolutely. And you know, witnessing a crash test , folks really come to understand the importance of these technologies. And like you said, the fact that these crash scenarios are the leading cause of fatalities is not lost on any of the visitors that come to TTI. But interestingly, when I joined TTI in 2016, I was completely blown away by the level of science, engineering, and technology required to ensure the safety, repeatability, and consistency of crash tests. And you break down for our listeners the painstaking detail necessary to conduct crash tests. I mean, how do the vehicles get to certain speeds and certain angles? And in addition to learning whether roadside safety hardware performs as expected, what else do you measure and monitor?
• 6:56
  Roger Bligh: Yeah, those are good questions. Let's consider a barrier system as an example for discussion. After the design of that barrier has been completed, we construct a prototype of the barrier at our proving grounds and then a vehicle of some prescribed body style, you know, according to our standard is purchased and prepped and instrumented. And then what we do is, we use a tow vehicle. And the tow vehicle is used to pull the test vehicle up to the designated impact speed using a tow cable and some pulleys and a separate guide cable, which is tensioned up along the path of the vehicle. It feeds through a guide arm attached to the front wheel of the test vehicle, and that serves as a form of external steering, and it helps guide the vehicle into the barrier at the desired location and angle. And then both of those cable systems, the tow cable and the guide cable, they release from the vehicle prior to impact, and it leaves that vehicle unrestrained and free to react with the barrier system.
• 7:55
  Greg Winfree (Guest Host): So I've seen several tests of course, and you utilize different angles and velocities. What's the science behind that or the rationale? How were they selected, and what are the range of performance parameters that need to be passed for a system to be successful?
• 8:14
  Roger Bligh: Yeah , so the standard does prescribe certain speeds and angles that we use to evaluate the hardware. So it's a performance standard, and we run those tests to a prescribed matrix. And some of the details of those tests such as the speed and the angle that we use for our barrier systems, they actually originate with a review of real-world crash data. So we periodically will look at that crash data and reconstruct some of those crashes to understand what the impact speeds and angles are. And from that information, we're able to develop a distribution for impact speed and impact angle and then select a percentile that we feel is appropriate for design purposes, and that information gets fed into our standard.
• 9:00
  Greg Winfree (Guest Host): Okay. Now, we didn't talk a significant amount about some of the pre-work that's done in the Center for Computational Mechanics. Maybe a little bit about how you all use simulation to suss out tests even before the physical test is conducted.
• 9:16
  Roger Bligh: Yes. So in fact, I mentioned that part of what our program does is we're not just testing these barriers, but we're also designing them. And the computer simulation is a tremendous tool that we have available to us to help in that design process. So what we can do is we can actually model the roadside safety hardware system that we're evaluating if it's a barrier or something else. And we also have finite element models of these test vehicles. And so we're able to, on the computer, before we ever go out to our test track, we're able to help determine the predicted impact performance of a particular system. And that helps us to perhaps make some design changes before we get to the test track or even optimize the design. And so the computer simulation has become an extremely valuable tool for us in the overall process of designing hardware and getting it out onto our roadways.
• 10:12
  Greg Winfree (Guest Host): Right. Well in addition to bragging about the prowess of your team and the work that you do, why don't you talk a little bit about the scanning and the disassembly of vehicles so that you get all of the parameters needed so that the computer simulation is successful, which then means the physical test is more likely to be successful?
• 10:35
  Roger Bligh: Right. So that goes to that modeling process that I was mentioning and the fact that we need models of our design vehicles right for use in these computer simulations. And so those vehicle models are typically developed through a reverse-engineering process. We basically disassemble the entire vehicle and we essentially scan in all of these different components and then eventually put them back together. And so we're looking at all of the key features of a vehicle and even the connection between these parts such as where the spot welds are and the different types of connections. And we also develop material properties through some physical coupon testing. And so all of that goes into the construction or development of a vehicle model that we can use to help assess the performance of our hardware through the development of the hardware models that I mentioned.
• 11:28
  Greg Winfree (Guest Host): Now, that's just tremendous work and that's why I wanted to drill down so that our listeners really understand how complex this undertaking is. So I'd like to reflect back on a crash test from last June. And for our listeners, we will be attaching a link to the video of the crash test that we're discussing today in the show notes. Your team tested an EV against the heavy duty guardrail. Now what were the reasons behind selecting that particular type of roadside safety hardware?
• 11:57
  Roger Bligh: Yes. Well, prior to that test that we performed some of our colleagues at the Midwest Roadside Safety Facility at the University of Nebraska, they had performed two crash tests on a standard, what we refer to as W-beam guardrail system using electric vehicles. And so the W-beam guardrail, that's the most commonly used guardrail system across the country, it's what you're probably seeing on your roadside is a metal beam on some posts. And it's been shown to be MASH compliant through separate full-scale crash testing. So the EV tests of the W-beam guardrail, they were performed with a rivian R1T pickup truck and a Tesla Model 3 passenger car. And both of those tests were performed at a nominal speed of 62 miles an hour and an angle of 25 degrees, which are the impact conditions that correspond to the MASH document that I mentioned for what we call test level three, which is the basic test level defined for passenger vehicles on our high speed roadways. Well, the Rivian pickup truck actually ruptured and went right through the W-beam guardrail system. And then the Tesla, which is a smaller vehicle, was actually a pretty interesting test. The Tesla Model 3 actually underrode the W-beam guardrail. So we had two failures of the W-beam guardrail system that kind of informed us prior to us performing our test.
• 13:26
  Greg Winfree (Guest Host): That's very eye-opening. So if previous tests demonstrated that a standard W-beam guardrail couldn't contain and redirect the EV, I mentioned that it was a heavy-duty guardrail, but specifically what kind of guardrail did you test this summer?
• 13:40
  Roger Bligh: Right. Well, given the failure of the W-beam TTI decided to test, as you mentioned, a stronger, more robust guardrail system. And that system is referred to as a thrie beam guardrail. And the thrie beam rail element is deeper compared to the W-beam, right. And so for instance, the thrie beam is 20 inches deep, whereas the W-beam is 12 inches deep, it actually had the effect of reducing the ground clearance, the height from the ground to the bottom of the rail. And so we thought that would be helpful in addressing that underride behavior that we observed in the W-beam guardrail test with the Tesla. And so the deeper thrie beam, it also has a greater cross-sectional area, so that means that it's stronger than the W-beam. So this thrie beam was also successfully crash tested under MASH criteria, and it was considered the next level of guardrail to evaluate with EVs.
• 14:35
  Greg Winfree (Guest Host): Mm-hmm. So consistent with what Nebraska-Lincoln utilized--the vehicle they used -- it sounds like we also used a Tesla Model 3 so that we could compare apples to apples. But what were the results of the tests this summer?
• 14:48
  Roger Bligh: So you are absolutely correct. We did use a Tesla Model 3 in this particular test, and we used the same impact conditions. And it was to be able to assess how this thrie beam guardrail would perform under those test level three conditions, you know, with that particular vehicle. Well, during that test with the Tesla, the vehicle kind of began to wedge under the thrie beam rail. It kind of compressed the bottom edge of the rail upward and eventually ruptured the rail and went through the thrie beam guardrail. And this was really unexpected because the impact severity of the Tesla was within the range of the current MASH testing criteria. Mm-hmm . So we didn't really view this as a strength test with the pickup truck. We were trying to evaluate that underride behavior with the smaller Tesla car. And so one of the reasons that surprised us is because we had seen the thrie beam work with other types of heavier vehicles over the years, including a single unit truck and even a bus. And I'd never seen a thrie beam guardrail rupture during my 38 year career.
• 15:56
  Greg Winfree (Guest Host): So what in particular about the EV--or is it specific to the Tesla?--but what might explain those results? I mean, how does the weight, center of gravity materials, and construction compare to standard sedans with internal combustion engines?
• 16:11
  Roger Bligh: Oh , that, that's a great question. I think it's very important to point out, this is not a Tesla problem. This is an EV problem, right? And we know there are many characteristics of EVs that are different from their internal combustion engine (or ICE) counterparts. And there are certain key differences that affect the compatibility of EVs with roadside barriers. So you mentioned that the EVs are considerably heavier than their ICE counterparts. You know, for example, a Ford Lightning EV pickup weighs 2,000 pounds more than the conventional Ford F-150 pickup.
• 16:46
  Greg Winfree (Guest Host): Wow.
• 16:47
  Roger Bligh: And that increase in weight, it places a lot more demand on our barrier systems. And so a barrier that might be near its performance limits under the MASH standard, it may fail when impacted by the heavier EVs. Mm-hmm . Mm-hmm . And you also mentioned, Greg, the center of gravity height. And that's another key difference. So the weight and position of the batteries in these EVs, right, it lowers the center of gravity height compared to a traditional ICE vehicle. Think about these batteries forming kind of a skateboard type of arrangement underneath the occupant compartment. Well, although that can help stabilize a vehicle compared to a normal ice counterpart, it can also increase the potential for that vehicle underride. And it's that type of underride behavior that we saw with the guardrail test. And it was also a partial factor in the thrie beam failure as well. And there's some other properties that can contribute to these undesirable test results that we've seen. And those include the crush stiffness of the EV and the profile of the EV. So we don't have a conventional engine compartment and there's no front engine. So the crush profile in the front quarter panel area that interacts with the barrier, it's considerably different. And that can permit the guardrail elements to intrude further into the occupant compartment and interact with other components such as the wheels that can maybe initiate tears in the guardrail.
• 18:12
  Greg Winfree (Guest Host): Mm- hmm . Well, knowing that Tesla's sister organization is SpaceX, are they also utilizing space-age materials or anything else exotic that might even be another factor for consideration?
• 18:25
  Roger Bligh: Well, certainly can be. The design of those vehicles is different from a geometric standpoint. The roofs of those vehicles, they tend to be all glass. So there are some other differences compared to our ICE vehicles. Certainly the battery compartments down there, really rigidize parts of the frame. So there's a lot of other smaller differences that can also contribute to how these vehicles interact with our roadside safety hardware. And we really need to get a better grasp on that and start looking at how we can maybe improve that interaction.
• 18:59
  Greg Winfree (Guest Host): Understood. Well, you know, I did some quick online research and discovered that there were almost 250,000 EVs on Texas roadways and an estimated 3.3 million EVs on the roads nationwide. So what are some of the implications of these results as more EVs are taking to the road across the country?
• 19:18
  Roger Bligh: Right. We know these vehicles are increasing in number. It's not a matter of if this is going to occur, it's occurring now. Right. And as these numbers of EVs continue to grow, the exposure in terms of the number of vehicle miles traveled also increases. And this is going to lead to an increase eventually in the number of crashes, including crashes with roadside safety barriers. And so if this EV compatibility with barrier systems is not addressed, it can result in an increase in the number of serious injury or fatal crashes that we might see with barrier systems in the future.
• 19:57
  Greg Winfree (Guest Host): Well, let me ask another question. So what happens next from a development perspective in terms of different vehicle tests or new kinds of hardware that can sustain impacts from increasing vehicle weights?
• 20:09
  Roger Bligh: Right. Well, our current MASH standard that we've been talking about today, it does not address EVs yet. It takes time for these standards to be updated to reflect changes in vehicle technologies and other areas. But that doesn't mean that we shouldn't be looking at this problem now. Right? We have identified that there is a compatibility problem between EVs and some of our existing roadside barrier systems. And we know that the number of EVs in our roadways is going to continue to grow. So what we need are new barrier solutions that are compatible with EVs. We need to develop and test and implement those barriers to help address this safety issue that we've identified. And I should note that the safety hardware for EVs, as we develop that, I think it's also going to have an added benefit in terms of accommodating our heavier conventional engine vehicles, our ICE vehicles, that are currently not addressed by our testing standard. Because there's a general trend, not just with EVs, but also with our ICE vehicles of increasing mass, increasing weight. And so as we start addressing the EV problem that we've identified and implementing barrier solutions for EVs, we'll have an added benefit in that area as well.
• 21:27
  Greg Winfree (Guest Host): Okay. Well, Roger , you've been doing this kind of work for a long time, but it's clear to me that you're still energized by it. What are some of the reasons you're ready to come into work each day?
• 21:37
  Roger Bligh: Right, well, my biggest motivation is the safety aspect of my work. And I feel like most of us have been impacted by a vehicle crash in some way. I know that I have. I often think about how something I do today could possibly save a life in the future, and that's very empowering. So I always say, you know, hopefully most of us will not have to rely on a roadside barrier or a safety device in our lives, but if you do, I'm gonna do my best to try and ensure that it's there and ready for its job if you need it.
• 22:11
  Greg Winfree (Guest Host): Well, those are tremendous parting words and truly a mission-oriented approach that is greatly appreciated. So Dr. Roger Bligh, thanks for joining me to talk about the important work TTI is doing to keep up with the never-ending changes in the vehicle fleet here in Texas and around the nation.
• 22:30
  Roger Bligh: Well , it's been a pleasure, Greg, and I really appreciate you having me. Thank you.
• 22:35
  Greg Winfree (Guest Host): So folks, in addition to exploring the safety implications of more electric vehicles on our roadways, researchers at TTI are also engaged with sponsors to determine how EVs can reduce transportation sector emissions and related health effects, and how EV adoption will affect our electric grid and our transportation funding methods. Although the majority of road users don't realize it, they owe a huge debt of gratitude to the world-class researchers at TTI and other institutions whose mission is to ensure that the road-going public gets home safely. Thanks for listening. Please take just a minute to give us a review, subscribe and share this episode. I invite you to join us next time for another conversation about getting ourselves and the stuff we need from point A to point B. Thinking Transportation is a production of the Texas A&M Transportation Institute, a member of The Texas A&M University System. The show is edited and produced by Chris Pourteau. This is Greg Winfree, signing off. Thanks again for joining us. We'll see you down the road.