What Causes Car Accidents?Author / Coordinator: Texas Transportation Institute
Texas Transportation Institute
The dictionary defines accident as "an unexpected and undesirable event, a mishap unforeseen and without apparent cause." Strictly speaking, most accidents are not accidents at all: they are collisions that could and should have been avoided. So, what causes them, and how can you avoid them?
Four factors contribute to the vast majority of collisions. In ascending order they are:
1. Equipment Failure
2. Roadway Design
3. Poor Roadway Maintenance
4. Driver Behavior
Over 95% of motor vehicle accidents (MVAs, in the USA, or Road Traffic Accidents, RTAs, in Europe) involve some degree of driver behavior combined with one of the other three factors. Drivers always try to blame road conditions, equipment failure, or other drivers for those accidents. When the facts are truthfully presented, however, the behavior of the implicated driver is usually the primary cause. Most are caused by excessive speed or aggressive driver behavior.
1. Equipment Failure – Manufacturers are required by law to design and engineer cars that meet a minimum safety standard. Computers, combined with companies’ extensive research and development, have produced safe vehicles that are easy and safe to drive. The most cited types of equipment failure are loss of brakes, tire blowouts or tread separation, and steering/suspension failure. With the exception of the recent rash of Firestone light-truck tire failures, combined totals for all reported equipment failure accounts for less than 5% of all motor vehicle accidents.
(A) Brakes – Modern dual-circuit brake systems have made total brake failure an unlikely event. If one side of the circuit fails, the other side is usually sufficient to stop a vehicle. Disc brakes, found on the front wheels of virtually every modern vehicle, are significantly more effective than the older drum braking systems, which can fade when hot. ABS (Anti Blockier System) or anti-lock brakes prevent the wheels from locking up during emergency braking maneuvers, allowing modern vehicles to avoid many accidents that previously would have occurred.
(B) Tires – Today’s radial tires are significantly safer than the bias-ply tires of 25 years ago. They still, however, need attention regularly. Under inflation, the most frequent cause of tire failure, is considered the main culprit in the recent Firestone tire-failure fatalities. Uneven or worn-out tires are the next most serious problem and can also lead to tire failure. Uneven wear is caused by improperly balanced tires, or misaligned or broken suspensions. Remember, all that keeps you connected to the roadway is your tires. If you don’t check your own, have your mechanic check them every 5,000 miles.
(C) Steering & Suspension – Your suspension keeps your tires in contact with the roadway in a stable and predictable manner. Your steering enables you to go around road obstacles and avoid potential accidents. Even a safe, well-trained driver is helpless in the event of a steering or suspension system failure. Such failures are catastrophic, especially at high speeds. Have your suspension and steering systems checked out by a mechanic every 10,000 miles.
(D) With regular component inspections by trained individuals, equipment failures can be virtually eliminated.
2. Roadway Design – Motorists may blame roadway design for accidents, but it’s rarely the cause. Consultants such as the Texas Transportation Institute have spent years getting road barriers, utility poles, railroad crossings, and guardrails to their current high level of safety. Civil engineers, local governments, and law enforcement agencies all contribute to the design of safe road layouts and traffic management systems. State and federal governments provide guidelines to their construction, with design flexibility to suit local conditions. Roadways are designed by engineers with special consideration given to the following:
(A) Hazard Visibility – Permanent roadway hazards consist of intersections, merging lanes, bends, crests, school zones, and livestock or pedestrian crossings. Temporary hazards include road construction, parked or disabled vehicles, accidents, traffic jams, and wild animals (especially deer).
(B) Roadway Surfaces – Engineers can use different surfaces (for example, grooved pavement) depending on the environment, traffic speed, traffic volume, and location of the roadway (noise barriers). Roadway markings let drivers know about their ability to pass safely (dotted & double lines), the location of the roadway in inclement weather (reflective cats-eyes & stakes), and where road surface ends and the shoulder begins.
(C) Traffic Control Devices – Traffic light signals, speed limit signs, yield and stop signs, school & pedestrian crossings, turning lanes, police surveillance cameras, and traffic circles or roundabouts.
(D) Behavioral Control Devices – Built-in obstacles that limit the ability of a vehicle to travel, including crash barrels, speed bumps, pedestrian islands, raised medians, high curbing, guardrails, and concrete barriers.
(E) Traffic Flow – Interstate highways remain the safest roads because their flow of traffic is in one direction. One-way streets ease traffic congestion in city centers as well. Rural two-lane roadways are statistically the most dangerous because of a high incidence of deadly head-on collisions and the difficulty impatient drivers face while overtaking slower vehicles.
(F) Roadway Identification Signs – enable someone without a detailed map to travel from one place to another. They give advance notice of intersections, destinations, hazards, route numbers, mileage estimates, street names, and points of interest.
(G) Weather – inclement conditions can aggravate existing hazards and sometimes create new road surfaces (ice & snow).
3. Poor Maintenance – Roadway maintenance contributes to some motor vehicle accidents, but not to the extent that drivers use it as an excuse. Unfortunately maintenance schedules and procedures vary greatly from city to city and state to state, so nationwide standards don’t exist. Below we outline some potential roadway maintenance shortcomings that you should be aware of.
(A) Debris on the roadway can be a problem, and is the responsibility of local highway departments.
(B) Faded road signs, and signs obscured by foliage, occasionally contribute to accidents. If you know of any offending signs, contact your local police department to see if they can get the problem remedied.
(C) Potholes cause a small number of accidents (primarily tire & suspension failures), but the accidents usually occur at low speeds and don’t cause many injuries. Call the police to get large dangerous holes attended to. Some Northern US cities have pothole complaint lines that are active during the winter and spring.
(D) Roadway construction is an oft-mentioned reason for accidents. Again the blame usually rests on aggressive drivers who are unwilling to merge or slow down when approaching a construction zone. In most states, fines are doubled in work zones, making it expensive as well as unsafe to speed. Stop-and-go traffic requires thoughtful, alert driving to avoid a collision with the car in front of you. Too often we worry that someone will cut in front of us in a traffic jam. The real problem is that drivers forget about the vehicle directly in front, rear-ending it while looking in their rearview mirror or daydreaming. Leave plenty of room between your car and the one directly in front of you. Our 3-second rule applies to traffic jams as well. If a few people cut in front of you, let them.
(E) Salting & Sanding – Many wintertime accidents are blamed on inadequate salting or sanding of icy roadways, but as so often, the real culprit is usually excessive speed. And salting only works if the ambient temperature stays above the middle teens. Recent environmental concerns have curbed widespread salting in recent years so less effective materials like clay, sand, and soot have replaced it in some areas. The fact remains that if highways are icy, speed needs to be reduced whether the roadway is salted or not.
4. Driver Behavior – Humans tend to blame somebody or something else when a mistake or accident occurs. A recent European study concluded that 80% of drivers involved in motor vehicle accidents believed that the other party could have done something to prevent the accident. A miniscule 5% admitted that they were the only one at fault. Surveys consistently reveal that the majority consider themselves more skillful and safer than the average driver. Some mistakes occur when a driver becomes distracted, perhaps by a cell phone call or a spilled cup of coffee. Very few accidents result from an ‘Act of God,’ like a tree falling on a vehicle.
Speed Kills – The faster the speed of a vehicle, the greater the risk of an accident. The forces experienced by the human body in a collision increase exponentially as the speed increases. Smart Motorist recommends that drivers observe our 3 second rule in everyday traffic, no matter what your speed. Most people agree that going 100 mph is foolhardy and will lead to disaster. The problem is that exceeding the speed limit by only 5 mph in the wrong place can be just as dangerous. Traffic engineers and local governments have determined the maximum speeds allowable for safe travel on the nation’s roadways. Speeding is a deliberate and calculated behavior where the driver knows the risk but ignores the danger. Fully 90% of all licensed drivers speed at some point in their driving career; 75% admit to committing this offense regularly.
Consider this example: a pedestrian walks out in front of a car. If the car is traveling at just 30 mph, and the driver brakes when the pedestrian is 45 feet away, there will be enough space in which to stop without hitting the pedestrian. Increase the vehicle speed by just 5 mph and the situation changes dramatically. At at 35 mph, with the pedestrian 45 feet away and the driver braking at the same point, the car will be traveling at 18 mph when it hits the pedestrian. An impact at 18 mph can seriously injure or even kill the pedestrian.
Who are the bad drivers? They are young, middle-aged, and old; men and women; they drive luxury cars, sports cars, SUVs and family cars. Almost every qualified driver I know admits to some type of risky driving behavior, most commonly speeding.
Aggressive Drivers – As we’ve described, modern cars are manufactured to very safe standards, and the environment they’re driven in is engineered to minimize the injuries suffered during an accident. The most difficult area to change is aggressive driver behavior and selfish attitudes. A 1995 study by the Automobile Association in Great Britain found that 88% of the respondents reported at least one of the behaviors listed below directed at them (in order of descending frequency):
(A) Aggressive tailgating
(B) Lights flashed at them because the other motorist was annoyed
(C) Aggressive or rude gestures
(D) Deliberate obstruction — preventing them from moving their vehicle
(E) Verbal abuse
(F) Physical assault
The same group were then asked about aggressive behavior they had displayed towards other drivers. 40% indicated that they had never behaved aggressively towards another driver. A further 60% of the survey respondents admitted to one or more of the following behaviors (listed in order of descending frequency):
(A) Flashed lights at another motorist because they were annoyed with them
(B) Gave aggressive or rude gestures
(C) Gave verbal abuse
(D) Aggressively tailgated another motorist
(E) Deliberately obstructed or prevented another from moving their vehicle
(F) Physically assaulted another motorist (one positive response)
These behaviors are probably under-reported, since most people are not willing to admit to the more serious actions, even if no penalty exists. The majority of these incidents happened during the daylight hours (70%), on a main road (not freeway or divided highway).
NYS Police characterize aggressive driving by the following traffic violations:
(A) Excessive speed
(B) Frequent or unsafe lane changes
(C) Failure to signal
(E) Failure to yield the right of way
(F) Disregarding traffic controls
(G) Impaired driving
The NYS State Police point out that there is a difference between aggressive driving and "road rage." Road Rage behaviors, such as using the vehicle as a weapon or physically assaulting a driver or their vehicle, are not aggressive driving. They are criminal offenses, and there are laws in place to address these violent crimes.