Road incidents are caused by large number of human factors such as failing to act according to weather conditions, road design, signage, speed limits, lighting conditions, pavement markings, and roadway obstacles. A 1985 study by K. Rumar, using British and American crash reports as data, suggested 57% of crashes were due solely to driver factors, 27% to combined roadway and driver factors, 6% to combined vehicle and driver factors, 3% solely to roadway factors, 3% to combined roadway, driver, and vehicle factors, 2% solely to vehicle factors, and 1% to combined roadway and vehicle factors. Reducing the severity of injury in crashes is more important than reducing incidence and ranking incidence by broad categories of causes is misleading regarding severe injury reduction. Vehicle and road modifications are generally more effective than behavioral change efforts with the exception of certain laws such as required use of seat belts, motorcycle helmets, and graduated licensing of teenagers. Human factors A side<unk>  after a driver misjudged his time to make a left turn Human factors in vehicle<unk> s include anything related to drivers and other road users that may contribute to a<unk> . Examples include driver behavior, visual and auditory acuity, decision-making ability, and reaction speed. A 1985 report based on British and American crash data found driver error, intoxication, and other human factors contribute wholly or partly to about 93% of crashes. A 2019 report from the U.S. National Highway<unk>  Safety Administration found that leading contributing factors for fatal crashes included driving too fast for conditions or in excess of the speed limit, operating under the influence, failure to yield right of way, failure to keep within the proper lane, operating a vehicle in a careless manner, and distracted driving. Drivers distracted by mobile devices had nearly four times greater risk of crashing their cars than those who were not. Research from the Virginia Tech Transportation Institute has found that drivers who are texting while driving are 23 times more likely to be involved in a crash as non-texting drivers. Dialing a phone is the most dangerous distraction, increasing a drivers’ chance of crashing by 12 times, followed by reading or writing, which increased the risk by ten times. An RAC survey of British drivers found 78% of drivers thought they were highly skilled at driving, and most thought they were better than other drivers, a result suggesting overconfidence in their abilities. Nearly all drivers who had been in a crash did not believe themselves to be at fault. One survey of drivers reported that they thought the key elements of good driving were: * controlling a car including a good awareness of the car's size and capabilities * reading and reacting to road conditions, weather, road signs, and the environment * alertness, reading and anticipating the behavior of other drivers. Although proficiency in these skills is taught and tested as part of the driving exam, a "good" driver can still be at a high risk of crashing because: the feeling of being confident in more and more challenging situations is experienced as evidence of driving ability, and that 'proven' ability reinforces the feelings of confidence. Confidence feeds itself and grows unchecked until something happens – a near-miss or an accident. An Axa survey concluded Irish drivers are very safety-conscious relative to other European drivers. However, this does not translate to significantly lower crash rates in Ireland. Accompanying changes to road designs have been wide-scale adoptions of rules of the road alongside law enforcement policies that included drink-driving laws, setting of speed limits, and speed enforcement systems such as speed cameras. Some countries' driving tests have been expanded to test a new driver's behavior during emergencies, and their hazard perception. There are demographic differences in crash rates. For example, although young people tend to have good reaction times, disproportionately more young male drivers feature in<unk> s, with researchers observing that many exhibit behaviors and attitudes to risk that can place them in more hazardous situations than other road users. This is reflected by actuaries when they set insurance rates for different age groups, partly based on their age, sex, and choice of vehicle. Older drivers with slower reactions might be expected to be involved in more<unk> s, but this has not been the case as they tend to drive less and, apparently, more cautiously. Attempts to impose<unk>  policies can be complicated by local circumstances and driver behavior. In 1969 Leeming warned that there is a balance to be struck when "improving" the safety of a road. Conversely, a location that does not look dangerous may have a high crash frequency. This is, in part, because if drivers perceive a location as hazardous, they take more care.<unk> s may be more likely to happen when hazardous road or<unk>  conditions are not obvious at a glance, or where the conditions are too complicated for the limited human machine to perceive and react in the time and distance available. High incidence of crashes is not indicative of high injury risk. Crashes are common in areas of high vehicle congestion, but fatal crashes occur disproportionately on rural roads at night when<unk>  is relatively light. This phenomenon has been observed in risk compensation research, where the predicted reductions in<unk>  rates have not occurred after legislative or technical changes. One study observed that the introduction of improved brakes resulted in more aggressive driving, and another argued that compulsory seat belt laws have not been accompanied by a clearly attributed fall in overall fatalities. Most claims of risk compensation offsetting the effects of vehicle regulation and belt use laws have been discredited by research using more refined data. In the 1990s, Hans Monderman's studies of driver behavior led him to the realization that signs and regulations had an adverse effect on a driver's ability to interact safely with other road users. Monderman developed shared space principles, rooted in the principles of the woonerven of the 1970s. He concluded that the removal of highway clutter, while allowing drivers and other road users to mingle with equal priority, could help drivers recognize environmental clues. They relied on their cognitive skills alone, reducing<unk>  speeds radically and resulting in lower levels of road casualties and lower levels of congestion. Some crashes are intended; staged crashes, for example, involve at least one party who hopes to crash a vehicle in order to submit lucrative claims to an insurance company. In the United States during the 1990s, criminals recruited Latin American immigrants to deliberately crash cars, usually by cutting in front of another car and slamming on the brakes. It was an illegal and risky job, and they were typically paid only $100. Jose Luis Lopez Perez, a staged crash driver, died after one such maneuver, leading to an investigation that uncovered the increasing frequency of this type of crash. Motor vehicle speed An accident on Ring I in Helsinki, Finland on August 25, 2006, at around 13:00 local time. The incident causes<unk>  congestion. The U.S. Department of Transportation's Federal Highway Administration review research on<unk>  speed in 1998. The summary says: * The evidence shows the risk of having a crash is increased both for vehicles traveling slower than the average speed, and for those traveling above the average speed. * The risk of being injured increases exponentially with speeds much faster than the median speed. * The severity / lethality of a crash depends on the vehicle speed change at impact. * There is limited evidence suggesting lower speed limits result in lower speeds on a system-wide basis. * Most crashes related to speed involve speed too fast for the conditions. * More research is needed to determine the effectiveness of<unk>  calming. In the U.S. in 2018, 9,378 people were killed in motor vehicle crashes involving at least one speeding driver, which accounted for 26% of all<unk> -related deaths for the year. In Michigan in 2019, excessive speed was a factor in 18.8% of the fatalities that resulted from fatal motor vehicle crashes and in 15.6% of the suspected serious injuries resulting from crashes. The Road and<unk>  Authority (RTA) of the Australian state of New South Wales (NSW) asserts speeding (traveling too fast for the prevailing conditions or above the posted speed limit) is a factor in about 40 percent of road deaths. The RTA also say speeding increases the risk of a crash and its severity. On another web page, the RTA qualify their claims by referring to one specific piece of research from 1997, and writes "research has shown that the risk of a crash causing death or injury increases rapidly, even with small increases above an appropriately set speed limit." The contributory factor report in the official British road casualty statistics show for 2006, that "exceeding speed limit" was a contributory factor in 5% of all casualty crashes (14% of all fatal crashes), and "traveling too fast for conditions" was a contributory factor in 11% of all casualty crashes (18% of
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