U.S Light Duty Vehicle (LDV) Performance Trends and Implications for Safety

MIT Mobility Initiative Research Briefing

The below report has 3 interactive storyboards built into the dashboard. While the default views are used to explain the findings and insights, we encourage readers to experiment with the filters and discover findings of their own.

Key Findings

The gap in braking performance (70mph - 0 in feet) of SUVs/pickup trucks versus the rest of the LDV fleet gets worse as the acceleration (0 - 60mph in seconds) gets faster and heavier.
BEVs on average accelerate much faster from 0 - 60 mph compared to other LDVs but do not have comparable braking performance; this gets amplified when looking at the top 50 percentile of accelerating BEVs.
With the LDV fleet comprising more SUVs/pickup trucks today and BEVs in the future, the combination of inadequate braking coupled with faster acceleration and heavier weight can considerably worsen road safety.

Background & Motivation

This report takes a data-driven look at the performance characteristics of Light Duty Vehicles (LDVs) such as acceleration in seconds (0 - 60 mph), braking in feet (70 mph - 0) of various powertrains, body type & style, MSRP, and Curb Weight to arrive at insights that can be used by both consumers in making more informed decisions and by policy-makers in designing a transport funding and regulatory framework that takes vehicle and road safety into account .

We are currently in the midst of three critical changes:

Decarbonizing Transportation - According to the US EPA the transportation sector is the largest GHG emitter in the US (at 28% in 2022) and it is the only sector where emissions have grown over previous years. Within transportation, LDVs are the largest source of emissions at 57%. Thus, it is critical to decarbonize this sector quickly. We are seeing a plethora of different powertrain options such as Battery Electric Vehicles (BEVs), Plug-in Hybrid Vehicles (PHEVs), Fuel Cell Electric Vehicles (FCEVs), and Hybrid Vehicles (HVs) being offered by manufacturers in this transition from Internal Combustion Engine (ICE) powered vehicles. In 2023, according to the US EIA, ICE sales still dominated at 84%. Non-ICE (BEV, PHEV, HV) sales were at 16% but growing much faster. Different powertrains come with their own advantages (efficiency, acceleration) and drawbacks (weight, range, refuel/recharge time, cost). By looking at actual performance data among all the currently available types of vehicles, we hope to provide new and insightful levels of analysis.
Road Safety - After many decades of healthy decline, deaths in the US due to motor vehicle crashes started rising again around 2015. This increase is both in absolute numbers and deaths per million miles. This is even worse if we look at pedestrian crash deaths which have risen roughly 89% since 2010: over 7500 pedestrians died after being struck by a vehicle in 2022 (GHSA and NHTSA FARS). This does not even include the number of injuries due to such incidents which is several fold higher than the number of fatalities. Many factors are being blamed for the increases in fatalities – drivers distracted by their phones, heavier cars, higher cars, distracted pedestrians, more active modes of mobility mixing with car traffic, roads that are designed purely for throughput of cars and not access for pedestrians or cyclists. While we cannot assess all of these factors in this research brief, we will look at the vehicle data to shed some light on this increase, which may open pathways to mitigate the cause.
Increasing Vehicular Speed - Vehicular speed is directly proportional to acceleration - higher acceleration makes the vehicle reach higher speeds faster. Higher acceleration has its benefits: reaching highway speeds and merging onto the freeway is easier, passing a slow moving car on a rural road is safer, and maintaining highway speeds with a more powerful motor is generally more efficient. But how fast is “fast enough” is still an open question, and has the fleet average reached a point at which this acceleration gets dangerous and irrelevant from a practicality standpoint, is something that needs to be addressed by policy makers and automotive manufacturers.
Thanks to the proliferation of electronic fuel injection in the 1980’s, variable valve timing in the 1990’s and forced induction in the 2000’s, engine outputs (and as a result the acceleration of cars) have been increasing. From around 12 seconds in the 1980’s the average 0 - 60 mph time in seconds for the LDV fleet has been halved to around 6 seconds. The trend is visualized in Figure 1, which is derived from the data web scraped from 0-60 Specs. This has been cross-checked with alternate sources such as Hyper Tuned who have analyzed 1100 cars to arrive at a current LDV fleet average of 6.1 seconds.

Figure 1. Average LDV Fleet 0 - 60 mph Time in Seconds by Year from 1960-2024

Why does this matter?

Newer cars with high horsepower, quick-shifting automatic transmissions, electric assist or full BEVs (with full torque available on tap when accelerating from standstill) make accessing this quick, seamless acceleration much easier (and quieter) as compared to cars from just a few years ago. A few seconds on the accelerator pedal can have the car running at unsafe speeds for the environment it is in, both for those in and outside the car. This can be dangerous as cars now mask speed so well and make quick acceleration so much of a non-event, leading the driver to not realize that they are going 20 or 30 mph over the speed limit. A second or two of additional throttle pedal pressure can lead to dangerous situations where they find themselves carrying more speed than anticipated and having to brake hard to avoid a mishap. One can anticipate a variety of scenarios where a driver miscalculates their vehicle’s acceleration, miscalculates gaps between vehicles, and/or miscalculates speed within a speed-limited environment. These miscalculations lead inevitably to dangerous, sometimes fatal, outcomes.

Hence, it is logical to expect that faster accelerating cars irrespective of shape, size or drivetrain type, must provide better braking performance as well, to help shed this easily gained speed effectively, and not exacerbate road safety issues. This should not be relegated to just performance coupes, hatchbacks and sedans. This has usually been the case and automotive manufacturers have put better and more robust braking hardware on their faster accelerating cars (BMW M, Audi RS , Mercedes AMG, Honda Type-R, Hyundai N, etc.) compared to the slower accelerating ones of the same model type. Due to many factors such as increasing SUV share of market, electrification of drivetrains, fast accelerating models are now available across many more model types (SUVs, pickup trucks, minivans) and different vehicle sizes and weights. The vehicle miles traveled (VMT) by these heftier and faster accelerating mainstream vehicles that are being used for regular commuting and other daily tasks is increasing by the day, as a result. Hence, a comprehensive analysis needs to be done if this trend of better braking performance for faster accelerating vehicles holds true or not, and if not how large is the difference and what could the possible safety implications be. The rest of this report will focus on the trend between acceleration and braking performance for different vehicle types, drivetrains, cost and weight*.

Data Collection

Multiple sources of data were webscraped and/or manually entered, and then carefully merged to create the vehicle database on which analysis was performed. Table 1 below summarizes the source, method of data collection and types of data collected from each source.

Source	Method	Data Points
0-60 Spec	Web Scraping	0 - 60 mph in seconds
Car & Driver	Manual	70 mph - 0 Braking in feet, 0 - 60 mph in seconds
CarSheet.io	Web Scraping	Model Year/Trim, Price, Body Style/Type, Dimensions, Weight, Powertrain type, Capacities, Features, Range, Warranty, Safety
Motor Trend	Manual	0 - 60 mph in seconds
NHTSA Safer Car Data	CSV Sheet	Rollover Ratings

Table 1: Data Source, Methodology & Points

Other points:

Car & Driver was preferred for the models where acceleration data was present from both Motor Trend and Car & Driver. The Car & Driver database was more complete, and hence we chose it as our primary source. In cases where acceleration data for a particular vehicle or trim did not exist at Car & Driver, we used data from Motor Trend.
Wherever possible and available we tried to include the 1-foot rollout in seconds to give a true realistic picture of the acceleration time, which has been the industry standard outside the US for a while.
Given that cruising speeds and speed limits on US highways are often 70 mph or more, we thought it was best to use the 70mph - 0 braking distance that Car & Driver uses, rather than the 60mph - 0 braking distance that Motor Trend uses. The braking data is for dry braking.
Car & Driver’s performance tests are very detailed, rigorous, consistent and, in our opinion, a good reference point for populating our performance data.
Over 360 car models and 500 trim levels from Model Year 2020 onwards were populated with this data for the analysis.
In our trend analysis below we set an upper limit of $150,000 for the MSRP.

Sport Utility Vehicles (SUVs) & Pickup Trucks

SUVs & Pickup Trucks have many safety drawbacks due to their heavy weight and tall form factor for both those inside and outside the vehicle. Many people assume that in a crash a SUV/Pickup will be safer to be in as it is heavier. While that may be true in isolation of other factors, when combined with those other factors we argue that an SUV/Pickup has lesser capacity to avoid a collision and higher tendency to rollover than a regular car.

Rollover - An analysis of the NHTSA rollover ratings shows that, for the Model Year 2023 LDV fleet, more than 95% of SUVs/Pickups are unable to score a 5/5 on this test whereas 80%+ of non-SUVs are able to achieve a perfect 5/5 score. The seven SUVs that score a 5/5 rating are all smaller, lower crossover SUVs – BEVs where the heavy battery pack is located at the bottom, assisting in the car’s safety. SUVs/Pickups, due to their top heavy nature, tend to roll over more. Crashes in which a vehicle rolled over accounted for 29% of all passenger vehicle occupant deaths in 2022, and the percentage of rollover fatalities for SUV/Pickup occupants is 1.6 (16% of all fatalities of SUVs/Pickups) to 1.9 (19% of all fatalities of pickups) times higher than that of regular cars (10% of all fatalities of cars) . While high wheel articulation, extra ground clearance, high seating is great for off-roading, most SUVs/Pickups are bought for regular commuting on paved roads. This excess metal, high center of gravity design leads to less efficient, slower and arguably more unsafe vehicles.

Collision Avoidance - It is not just the rolling over that is an issue. Being heavier translates to poorer braking and slower acceleration when merging onto the freeway. We analyze the LDV fleet for vehicles with an MSRP of less than $150,000 and separate out the body styles of SUVs and pickup trucks. On plotting the acceleration versus braking, a surprising trend is presented as seen in Dashboard 1 below.

One would assume that models and trims that accelerate faster would have better braking hardware to cope with the fast acceleration and help it shed speed faster. Analyzing the data in Dashboard 1 below, we can see that this certainly holds true for sedans, hatchbacks, wagons, and coupes that comprise the upwards sloping blue line, highlighting a good increase in braking performance for the faster cars . On the other hand, the orange line, which comprises SUVs/pickup trucks, stays relatively flat and is above the average braking distance line - which is for all LDVs. This means that faster SUVs/Pickups on average do not have the necessary braking performance to compensate for their faster acceleration i.e. they are nowhere near as efficient in shedding speed when compared to equally-fast cars that have 0 - 60 mph acceleration times faster than the average 6 seconds. This can have tremendous impacts on road safety fatalities as these vehicles are also much heavier (as is denoted by the size of the triangle/circle/square) and thus can cause much more damage when colliding with other vehicles and or vulnerable road users due to their poor ability to shed speed.

Dashboard 1 also separates the vehicles by size (square - large, circle - midsize, triangle - compact). As expected, the vehicles with the worst braking performance are large SUVs/pickup trucks (orange squares) most of which are above the average braking distance line. It would be prudent to point out that the few SUVs below the blue line are monocoque construction vehicles and are compact or midsize vehicles, represented by a triangle and circle respectively. The worst performing vehicles from a braking perspective, comprises mostly heavier, full-size SUVs/pickups, most of which have a ladder-frame chassis represented by a square. It is a known fact that monocoque chassis construction vehicles offer superior handling and braking and are lighter in weight when compared to ladder-frame chassis vehicles. While the intricacies of each chassis type are beyond the scope of this report, ladder-frame chassis vehicles are better at off-roading, hauling cargo, and military use and are usually compromised for normal on-road travel.

Dashboard 1. Braking vs Acceleration performance for SUV vs non-SUV vehicles

This gets even more serious if we consider the visibility issues and associated increase in fatalities due to higher front-ends of SUVs/Pickups – a 10 cm increase in the front-end height causes a 22% increase in pedestrian fatality. With almost 80% of new car sales annually coming from SUVs/Pickups (see figure 2 below), the share of full-size SUVs/pickups is increasing much faster – this is a problem that is bound to get worse, unless automakers and regulators put stringent guidelines and performance metrics in place.

Figure 2. Share of new LDV sales by Vehicle Type from 2010 - 2021

Battery Electric Vehicles (BEVs)

BEVs are excellent from an efficiency standpoint in converting stored energy into forward motion when compared to ICE vehicles. They also generate all their torque from a standstill, hence providing instant, seamless and uninterrupted acceleration. However, they are heavier than their typical ICE counterparts, largely because their batteries are heavy due to not being as energy dense as liquid fuel. Therefore, BEVs require larger battery packs to ensure decent range. As seen in the section above, weight penalizes the braking performance of SUVs heavily – how critical is it when looking at BEVs?

From our database the median 0 - 60 mph time for a BEV is 4.3s while it is over 6s for a non-BEV car. While the added performance is a great testament to the efficiency and power of a BEV drivetrain and serves as a great marketing point for the brochure, what remains to be seen is whether the braking performance matches this added acceleration for BEVs.

Dashboard 2 below shows that while the disparity in braking performance of BEVs (green circles) versus non-BEVs (red circles) is not as bad as that between SUVs versus non-SUVs, there is significant room for improvement. With most of the BEVs accelerating to 60 mph in under 4.5 seconds (a time which was deemed sportscar territory not too long ago), other than a handful most BEVs do not have the braking performance needed to cope with being such quick accelerating cars. The size of the circles denotes the horsepower rating. Again, we see that BEVs have far higher horsepower than their non-BEV counterparts, some of which is required as BEVs are heavier than their non-BEV counterparts. While it can be argued that making a BEV car more powerful and accelerate faster is easier than a non-BEV car, pursuing 0 - 60 mph time and not bestowing sufficient attention on overall braking safety and vehicle efficiency is probably not the correct north star to be focusing on.

The problem of inadequate braking with BEVs gets worse as seen in the dashboard if we filter the 0 - 60 mph time to under 3.8 seconds. 50% of the BEVs in our database (30 models out of 60) fall in this category which is significant. There is an additional 10 to 15 feet in the braking distance needed by these fast accelerating BEVs versus non-BEVs. As mentioned above for SUVs, this can have tremendous impacts on road safety fatalities as BEVs are heavier and can cause much more damage when colliding with other vehicles and/or vulnerable road users, due to their poor ability to shed speed.

Dashboard 2. Braking vs Acceleration performance for BEV vs non-BEVs

Weight

It is well established that heavier vehicles need more effort to stop given the additional momentum they carry. Vehicle manufacturers usually add bigger (e.g., larger rotors & pads, higher number of pistons in the brake calipers, larger brake booster) and more resilient (e.g., braided brake lines, high performance brake fluid) braking hardware, and utilize high performance wider tires among other things to help their performance oriented, heavier and more expensive, models brake better. As seen in Dashboard 3 below, for non-SUVs/pickups as the weight of the vehicle increases, the braking performance gets worse. This is even more prominent for BEV SUVs and pickups which are amongst some of the heaviest passenger vehicles on the road .

The heavier ones do not have better braking performance, possibly due to the braking hardware not being sufficiently upgraded to counter the added weight and height. As most of the large orange circles (high SUVs and pickups) are in the top right corner (heavy & poor braking), the braking performance of this segment clearly needs improvement. This is even more critical given the additional damage that these heavier vehicles with poor braking can cause to other vehicles and Vulnerable Road Users.

Dashboard 3. Braking performance vs Weight of the Vehicle

Key Takeaways

Road safety for both those in the vehicle and those outside the vehicle has been receiving a lot of attention in the US of late, and understandably so given the wrong direction fatalities are moving in. For a long time the focus was only on keeping the occupants safe, but we are seeing some movement from regulators on this. In April 2024, the U.S. Department of Transportation’s National Highway Traffic Safety Administration (NHTSA) finalized a standard requiring automatic emergency braking (AEB), including pedestrian AEB, standard on all passenger cars and light trucks by September 2029. This is expected to significantly reduce rear-end and (more importantly) pedestrian crashes.

The US lagged behind the EU and other regions of the world in moving from regular hi-lo beam headlights to adaptive headlights. Adaptive lights automatically manage the beam pattern and can illuminate the distant road in front of the driver similar to high beams highlighting pedestrians/cyclists, while also aiming the light away from oncoming traffic to prevent blinding oncoming drivers. In 2022, NHTSA finally approved the use of adaptive headlights, which can greatly reduce collisions during low-light conditions. This will greatly help reduce pedestrian and cyclist safety incidents which have been increasing of late, with most of this increase driven by incidents at night.

However, as we have seen above, many more policy and regulatory steps need to be taken to ensure the safety of those inside and outside the vehicle. A variety of factors should be considered, including the following -

Braking Performance of a vehicle needs to be included as part of the safety testing and possibly listed on the Window Sticker. This is critical as the consumer needs to be made aware of this aspect – if more expensive/faster SUVs are worth it even though they have poorer braking performance than cheaper/slower ones. The deviance of the vehicle model’s score from its category’s average and the LDV fleet average must be mentioned. These tests must be performed by a neutral agency (using tires and brake hardware that the car is sold with, regular road surface, regular brake fluid) and not the manufacturer, to ensure a fair rating process.
How fast is fast enough? This question is fairly subjective, and a regulator may not want to hamper possible technological progress in powertrain efficiency here by mandating slower accelerating cars. However, one must take into account that cars that accelerate rapidly wear out their tires faster, causing more particulate matter emissions, and obviously use up much more energy when they accelerate at full throttle. The default driving modes must be tuned for more sedate responses, especially when driving on city and suburban roads. Manufacturers must focus on efficiency, lighter curb weights and affordability if we are to succeed in the decarbonization transition.
Car Bloat and the increasing share of SUVs are well documented as causing a lot of the problems we associate with cars today from a safety and efficiency perspective. The work above clearly highlights the massive gap that exists in braking performance between fast accelerating SUVs and non-SUVs. Many cities and transport agencies are putting additional parking fees on SUVs and introducing weight based registration fees. They must also consider the additional safety risk associated with these fast-accelerating SUVs with unsatisfactory braking performance and add a suitable penalty and possible regulation at the federal level. With SUVs being the profit drivers for most automotive companies, it is even more critical that manufacturers address this gap in braking and safety, ensuring that consumers get a product with satisfactory overall performance and safety ratings.

Conclusion

This Report was designed to provide a data driven analysis of many different performance metrics and vehicle design factors for the LDV fleet, something which has not been done at this scale before. Different types of vehicles are designed for different purposes and working environments. Pickup trucks are immensely useful and effective in carrying and towing heavy loads, but we are increasingly seeing them replacing sedans and hatchbacks and being used exclusively for shopping errands and commuting, not hauling/towing. The effects of having the dominant vehicle on public roads being SUVs and pickups needs to be studied, and that is precisely what we have tried to do here. The data and analysis provides a clear picture on the inadequacies of the braking performance of SUVs/pickups when compared to what one pays or how fast it accelerates. Automotive companies have in the past shown that they can innovate and improve such metrics. GM’s full size SUV’s improved braking performance by almost 30% from the late 90’s to 2020. We hope consumers use this analysis to make an informed decision when purchasing a vehicle, and that regulators and policy makers use this to ensure stricter and more consistent performance and efficiency guidelines for the LDV fleet, in order to make the roads safer for everyone.

*Statistical Significance of the Data Analysis - We are aware that the R-square values are not very high for many of the trend-lines shown above. However, given that we are not looking to predict the response variable, but our main objective is to explain if the observed effect between the predictor (for e.g., Acceleration) and response variable (for e.g., Braking) is significant, we are not overly concerned about the small R-square values. We are more concerned here with the p-values, which in the views/storyboards we have shown above are less than the usual significance level of 0.05, indicating that the observed effects are significant. Please note, that as you change the filters of the dashboards above, the p-values and statistical significance can change.

While very effort has been taken to ensure comprehensiveness and accuracy of the US LDV fleet, given the sheer number of models/trims on sale and the frequency of updates, it is possible that a data point may have been missed or incorrectly tagged. We would greatly appreciate if readers can point out such errors and/or requests to update the data to Bhuvan Atluri or Aaron Zhu.