A skid mark is the visible mark left by any solid which moves against another, and is an important aspect of trace evidence analysis in

forensic science Forensic science, also known as criminalistics, is the application of science to criminal and civil laws, mainly—on the criminal side—during criminal investigation, as governed by the legal standards of admissible evidence and criminal ...

and forensic engineering. Skid marks caused by tires on roads occur when a vehicle wheel stops rolling and slides or spins on the surface of the road. Skid marks can be analyzed to find the maximum and minimum vehicle speed prior to an impact or incident.

Skid __NOTOC__ Skid or Skids may refer to: * Skid, a type of pallet * Skid (aerodynamics), an outward side-slip in an aircraft turn * Skid (automobile), an automobile handling condition where one or more tires are slipping relative to the road * Skid ...

ding can also occur on black ice or

diesel Diesel may refer to: * Diesel engine, an internal combustion engine where ignition is caused by compression * Diesel fuel, a liquid fuel used in diesel engines * Diesel locomotive, a railway locomotive in which the prime mover is a diesel engi ...

deposits on the road and may not leave a mark at all.

Characteristics

Skid marks are divided into "acceleration marks" created on acceleration, if the engine provides more power than the tire can transmit; "braking marks", if the brakes "lock up" and cause the tire to slide; or " yaw marks", if the tire slides sideways. Each skid mark has a characteristic appearance, and an experienced accident reconstructor or forensic engineer can often determine what the vehicle was doing by examining the marks left by the tire. Different road surfaces produce different kinds of skid marks, sometimes also referred to as ''scuff marks'' or ''tire marks''. On asphalt road surfaces, skid marks are usually the result of bituminous oils in the asphalt that are heated because of the friction of braking or accelerating and rise to the surface, leaving dark marks.Carty, G. Collision Reconstruction. Nov 3, 2016. Mississauga, ON : University of Toronto Mississauga. This kind of mark on asphalt can last for months or even a year or two if they are particularly dark and the roadway is not well traveled. On other road surfaces, such as concrete, the marks result from the deposition of tire compounds onto the surface of the roadway. This kind of skid mark is typical of airport runways, which need to be periodically cleaned to remove deposited debris that reduce the frictional coefficient of the runway.D.P. Eisenbeisz, Wikipedia Talk response. June 28, 2008.Miranda, M. Tire Marks & Their Role in Accident-Reconstruction Investigations. Jan 8, 2018. PInow.com. The durability of these marks depends on a number of factors, including road use, tire compounds, weather, and frequency of road cleaning. Braking marks will vary depending on whether the car uses ABS or not. If not, there will be two lines. The darker marks on the outside are from the front wheels, while the back tires leave thinner marks. This is because the force exerted makes the wheels take on a conical shape. If the car uses ABS, the marks will be much fainter as less heat is produced by the release-stop mechanism of ABS. Scuff marks may be visible however with ABS. The term "scuff mark" is more often used for marks left by rubber

shoe A shoe is an item of footwear intended to protect and comfort the human foot. They are often worn with a sock. Shoes are also used as an item of decoration and fashion. The design of shoes has varied enormously through time and from cultur ...

s on a floor, mainly sneakers or trainers leaving black rubber marks on a gymnasium floor or

basketball court In basketball, the basketball court is the playing surface, consisting of a rectangular floor, with baskets at each end. Indoor basketball courts are almost always made of polished wood, usually maple, with -high rims on each basket. Outdoor su ...

when someone comes to a hard stop, or pivots in place, or a hockey puck leaving a rubber streak along the edge boards of the rink.

Ladder accidents

Skid marks can also be formed where a

ladder A ladder is a vertical or inclined set of rungs or steps used for climbing or descending. There are two types: rigid ladders that are self-supporting or that may be leaned against a vertical surface such as a wall, and rollable ladders, such ...

suddenly slips and the user falls to the ground, especially if the ladder feet are faulty or absent. Loss of the

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

feet or foot causes the

aluminum Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...

stile to make contact with the ground, and if a hard surface like concrete or tiling, a skid mark shows how and why the ladder slipped. Unless fixed to the wall upon which they are leaning, ladders can slip down easily, especially if the ladder is leaned at an angle lower than about 75 degrees. Such slip accidents tend to happen when the user is near the top of the ladder, increasing his or her chances of serious personal injury.

Accident reconstruction

Such marks are important evidence for

vehicular accident reconstruction Traffic collision reconstruction is the process of investigating, analyzing, and drawing conclusions about the causes and events during a vehicle collision. Reconstructionists conduct collision analysis and reconstruction to identify the cause ...

, when their size and shape can reveal much about vehicle speed and forces of acceleration or deceleration. They are one form of trace evidence. They represent a form of contact evidence produced according to Locard's exchange principle. The length of the skid mark is usually closely related to the vehicle speed at the instant of braking, so measuring the marks yields an estimate of original speed.

Modern slang

In modern

slang Slang is vocabulary (words, phrases, and linguistic usages) of an informal register, common in spoken conversation but avoided in formal writing. It also sometimes refers to the language generally exclusive to the members of particular in-gr ...

, the term "skid mark" means a fecal stain or smear on the back of one's

underwear Undergarments, underclothing, or underwear are items of clothing worn beneath outer clothes, usually in direct contact with the skin, although they may comprise more than a single layer. They serve to keep outer garments from being soiled o ...

. It may also apply to a pet experiencing anal irritation and sliding (or scooting) across the floor to relieve the itching or obstruction, leaving a line of feces behind.

Notes

References

External links

Accreditation Commission for Traffic Accident Reconstruction (ACTAR)

National Highway Traffic Safety Administration

National Academy of Forensic Engineers
{{Tires, state=collapsed Tires Evidence law Forensic evidence