Tire Mark Evidence

What the Road Surface Records About Every Vehicle's Final Seconds

A tire mark on a roadway is a physical record of the forces acting on a vehicle at the moment the mark was created. It documents whether the driver braked, how hard, for how long, and whether the vehicle was traveling straight or rotating. It records whether the driver attempted to steer around a hazard, whether the vehicle lost traction, and whether the wheels were locked, rolling, or spinning. Each type of mark has distinct visual characteristics that allow a trained crash reconstructionist to identify the force that produced it, the direction the vehicle was traveling, and the speed at which the vehicle was moving when the mark began. In truck crash litigation, tire marks are among the most important categories of physical evidence because they provide an objective, physics-based record of driver behavior in the seconds before impact, during the collision, and in the post-impact trajectory.

Tire marks are also among the most perishable categories of crash evidence. On asphalt roadways, the marks are created by heat generated from friction between the sliding tire and the road surface, which brings tar to the surface and creates a visible darkening.^¹ On concrete surfaces, the marks consist primarily of rubber compound transferred from the tire to the pavement, producing lighter, less distinct markings that are harder to see and faster to degrade. Rain, traffic, road sweeping, and the simple passage of time erode the marks progressively. A set of skid marks that is clearly visible hours after a crash may be barely detectable days later and entirely gone within a week. The window for documenting tire mark evidence is measured in hours to days, not weeks, and the quality of the documentation at the scene determines the quality of the reconstruction that follows.

Types of Tire Marks

Tire marks fall into distinct categories, each produced by a different combination of forces acting on the tire. Correctly identifying the type of mark is essential because the physics used to calculate speed from a skid mark are different from the physics used to analyze a yaw mark, and misidentifying the mark type produces erroneous speed calculations.

Skid Marks

Skid marks are the most commonly recognized type. A skid mark is produced when a tire slides across the road surface without rotating, meaning the wheel is locked by braking force that exceeds the tire's grip on the pavement.^² The mark appears as a dark, continuous stripe on asphalt, with a width corresponding to the tire's contact patch. Skid marks begin abruptly where the wheel locked and end where the vehicle stopped, collided with another object, or the driver released the brakes. The length of a skid mark, combined with the coefficient of friction of the road surface, allows a reconstructionist to calculate the minimum speed of the vehicle at the point where the skid began using the drag factor equation, one of the foundational formulas in crash reconstruction.^³

Impending skid marks are produced when the braking force is high but not quite sufficient to lock the wheel entirely. The wheel is rotating slower than the vehicle is traveling, creating a partial slide that produces a lighter, less distinct mark than a fully locked skid. Impending marks often appear immediately before the onset of a locked skid, recording the transition from braking to wheel lockup. They indicate that the driver was applying significant braking force before the wheels locked, which is relevant to reaction time analysis.^⁴

Yaw Marks

Yaw marks are produced when a vehicle is rotating around its vertical axis while the tires are still rolling. This occurs when the vehicle enters a curve too fast, when the driver makes a sudden steering input, or when the vehicle loses directional stability. Yaw marks are distinguishable from skid marks by their curved path and by the presence of striations, which are narrow, parallel lines within the mark that indicate the tire was both rolling and sliding simultaneously.^⁵ The striations are perpendicular, or nearly so, to the vehicle's direction of travel, which allows the reconstructionist to determine the vehicle's yaw angle at each point along the mark.^⁶ Yaw marks can be used to calculate the vehicle's critical speed through the curve using the radius of the mark and the road's friction coefficient and superelevation.

Scrub Marks

Scrub marks, also called scuff marks or side-slip marks, are produced when a tire slides laterally across the road surface, typically at the moment of impact or during the post-impact trajectory when a vehicle is pushed sideways by collision forces.^⁷ Scrub marks at the point of impact are among the strongest indicators of the collision location because they are created at the instant the collision forces begin to act on the vehicle. A scrub mark that begins at a specific point on the roadway and extends in the direction the vehicle was pushed establishes both the point of impact and the direction of the applied force.

Acceleration Marks

Acceleration marks are produced when the drive wheels spin faster than the vehicle is moving, typically during aggressive acceleration from a stop or during loss of traction on a slippery surface. These marks begin with heavy, dark deposits and taper as the tire gains traction and the spinning decreases. Acceleration marks are relevant in cases where the driver's pre-crash behavior, such as aggressive acceleration from an intersection, is at issue.^⁸

Flat Tire Marks

Flat tire marks are produced when a deflated tire rolls along the road surface, creating a distinctive pattern that is wider than a normal tire mark and shows irregular edges from the tire's sidewall contacting the pavement.^⁹ These marks can establish that a tire was flat before the crash, which is relevant to determining whether a tire failure caused the crash or resulted from it.

How ABS Changes the Evidence

The widespread adoption of antilock braking systems on commercial trucks has fundamentally changed the tire marks that trucks leave on the roadway during emergency braking. ABS prevents the wheels from locking by rapidly modulating brake pressure, releasing and reapplying the brakes many times per second to keep the tire at the edge of its traction limit without sliding. This produces maximum braking efficiency, but it eliminates the continuous locked-wheel skid marks that traditional braking analysis depends on.

A truck equipped with a properly functioning ABS system will leave intermittent striping rather than a continuous dark skid mark during hard braking.^¹⁰ The marks appear as a series of short, closely spaced stripes or shadow marks where the tire momentarily approached lockup before the ABS released pressure. These intermittent marks are lighter, shorter, and less visible than conventional skid marks. In some conditions, particularly on dry pavement with a well-functioning ABS system, the truck may leave no visible tire marks at all during maximum braking.

This creates a significant investigative challenge. An investigating officer or reconstructionist who arrives at a crash scene and finds no skid marks may incorrectly conclude that the driver did not brake before the crash. The absence of visible marks on an ABS-equipped truck does not mean the driver did not brake. It may mean the ABS functioned as designed, preventing wheel lockup and eliminating the marks that would otherwise have been visible. Conversely, a truck with ABS that leaves a long, continuous skid mark from one wheel may have a malfunctioning ABS sensor or modulator at that wheel position, a finding that is relevant both to the braking analysis and to the carrier's vehicle maintenance obligations.^¹¹

The interaction between ABS and crash reconstruction has shifted the reconstructionist's reliance from tire mark analysis toward electronic data. The ECM and event data recorder capture braking data, including brake switch activation time, vehicle speed during braking, and the speed at impact, which provide the same information that skid mark analysis would have provided on a non-ABS-equipped truck. In modern crash reconstruction, the tire marks on the road and the electronic data from the truck are complementary sources that are cross-referenced against each other to produce a unified speed and braking analysis.

What Tire Marks Reveal About Load Condition

The characteristics of tire marks also provide information about the weight of the truck at the time of the crash. A fully loaded tractor-trailer leaves wider, darker tire marks than an empty truck braking on the same surface at the same speed, because the loaded truck's tires are under greater vertical load, which increases the contact patch area and the heat generated during sliding.^¹² The depth and intensity of a skid mark from a loaded truck are visibly different from those of an unloaded truck, and an experienced reconstructionist can make a preliminary assessment of whether the truck was loaded or empty based on the mark's appearance.

The load condition is directly relevant to the braking distance calculation. A loaded truck has greater momentum than an empty truck at the same speed, and it requires a longer distance to stop. The coefficient of friction between the tire and the road surface may also differ between loaded and empty conditions because the tire's contact patch and the vertical load on the tire affect the friction relationship. Reconstructionists account for these differences by adjusting the drag factor in the speed calculation to reflect the estimated or known weight of the vehicle.

The Perishability of Tire Mark Evidence

Tire marks on asphalt roadways degrade through several mechanisms. Traffic passing over the marks gradually erases them as other vehicles' tires rub against the deposited material. Rain washes away the tar and rubber residue that makes the marks visible. Road maintenance, including sweeping and repaving, eliminates marks entirely. Sunlight and temperature cycling cause the contrast between the mark and the surrounding pavement to fade. On high-traffic roads, a set of skid marks may be significantly degraded within 24 to 48 hours and undetectable within a week.^¹³

The implication for litigation is that tire mark evidence must be documented at the scene, ideally within hours of the crash, or it will be lost. Law enforcement officers who respond to the crash are typically the first to document tire marks, and the quality of their documentation determines whether the evidence is available for subsequent analysis. Best practice requires measuring each tire mark's length, width, location relative to lane lines and fixed reference points, and photographic documentation from multiple angles with scale references included in the images.^¹⁴

Modern scene documentation technologies, including total station surveying, 3D laser scanning, and drone-based photogrammetry, capture tire mark evidence with greater precision and completeness than traditional tape-measure methods. These technologies create permanent spatial records that preserve the exact location and geometry of every mark, allowing reconstructionists to re-measure and reanalyze the evidence throughout the litigation without returning to the scene.^¹⁵

The Regulatory Framework

Several federal regulations intersect with tire mark evidence and its analysis in truck crash litigation.

Under 49 C.F.R. § 393.40, every commercial motor vehicle must be equipped with brakes adequate to stop and hold the vehicle.^¹⁶ The braking performance standards in 49 C.F.R. § 393.52 establish specific stopping distance requirements for commercial vehicles based on their type and weight.^¹⁷ These stopping distance standards provide a regulatory baseline against which the braking performance documented by tire marks can be compared. A truck whose tire marks indicate a stopping distance that significantly exceeds the regulatory standard may have had a braking deficiency, whether from maladjusted brakes, worn linings, air system leaks, or ABS malfunction.

Under 49 C.F.R. § 396.3, the carrier must systematically inspect, repair, and maintain all vehicles subject to its control, with all parts and accessories in safe and proper operating condition at all times.^¹⁸ This obligation specifically encompasses braking systems, including ABS components whose proper functioning directly affects the tire marks the truck leaves during emergency braking. A carrier whose truck left a single continuous skid mark from one wheel while the other wheels left intermittent ABS marks has a vehicle with a detectable ABS malfunction that should have been identified and repaired during routine maintenance.

Under 49 C.F.R. § 396.13, the driver must conduct a pre-trip inspection of the vehicle before operation, and must review the previous driver's vehicle inspection report.^¹⁹ Brake performance is a required element of the pre-trip inspection. A driver who reports that the brakes felt soft, pulled to one side, or required excessive pedal effort has documented a braking deficiency that the carrier must repair before dispatching the vehicle.

Under 49 C.F.R. § 390.15, motor carriers must maintain an accident register and retain copies of all accident reports for three years.^²⁰ While this regulation does not require the carrier to document tire marks, the accident register confirms the carrier's knowledge of the crash and triggers the duty to preserve all evidence, including physical evidence at the scene. A carrier that arrives at the scene before law enforcement, documents the scene through its own rapid response team, and then fails to produce those photographs or measurements in discovery has potentially withheld relevant evidence.

Under Federal Rule of Civil Procedure 37(e), the consequences for failing to preserve electronically stored information extend by analogy to the broader duty to preserve physical evidence.^²¹ When a carrier's rapid response team photographs tire marks at the scene and those photographs are not produced in discovery, the failure raises spoliation concerns. The tire marks themselves are perishable evidence that the carrier had the opportunity to document and the obligation to preserve.

What Discovery Should Target

Discovery in a tire mark case should capture the scene documentation created by every party that recorded the physical evidence.

Key categories include:

The objective is to combine the tire mark evidence with the electronic data and the vehicle's known weight to produce a scientifically defensible reconstruction of the truck's speed, braking behavior, and trajectory in the seconds before the crash.

Sources

• [1] Los Angeles Police Department, Basic Collision Investigation Course.
• [2] Id.
• [3] Los Angeles Police Department, Basic Collision Investigation Course (Speed/Skid Chart and minimum-speed-from-skid-mark methodology).
• [4] Los Angeles Police Department, Basic Collision Investigation Course (impending skid mark definition).
• [5] Kurt D. Weiss, "Auto Accident Reconstruction: The Basics You Must Know," Plaintiff Magazine, November 2007.
• [6] Los Angeles Police Department, Basic Collision Investigation Course (yaw mark striation orientation relative to direction of travel).
• [7] Id.
• [8] Id.
• [9] Id.
• [10] Id.
• [11] 49 C.F.R. § 393.55, eCFR, current as of July 2026.
• [12] Kurt D. Weiss, "Auto Accident Reconstruction: The Basics You Must Know," Plaintiff Magazine, November 2007.
• [13] Transport Canada, Heavy Vehicle Event Data Recorders: Best Practices.
• [14] National Cooperative Highway Research Program, Transportation Research Board, scene documentation and evidence measurement guidance.
• [15] Federal Highway Administration, Unmanned Aircraft Systems, Report No. FHWA-HOP-20-063 (2020).
• [16] 49 C.F.R. § 393.40, eCFR, current as of July 2026.
• [17] 49 C.F.R. § 393.52, eCFR, current as of July 2026.
• [18] 49 C.F.R. § 396.3(a), eCFR, current as of July 2026.
• [19] 49 C.F.R. § 396.13, eCFR, current as of July 2026.
• [20] 49 C.F.R. § 390.15, eCFR, current as of July 2026.
• [21] Fed. R. Civ. P. 37(e).
• [22] National Highway Traffic Safety Administration, Model Minimum Uniform Crash Criteria (MMUCC).
• [23] 49 C.F.R. § 396.3(a), eCFR, current as of July 2026.