Crashes that cause injuries and/or property damage occur at the highest rates in urban areas. Crashes involving fatalities, however, are more likely to occur in rural areas. A 2003 Insurance Research Council study of a national sample of automobile crash injury claims found that about 75 percent of the crashes occurred in urban areas.¹ A 2006 report by the Highway Loss Data Institute examined insurance collision, property damage liability, and personal injury protection losses by vehicle density for 2003-05 model year vehicles.² Collision and personal injury protection claim frequencies were 39 percent higher in the most dense areas compared with the least dense areas. Property damage liability claim frequencies were 32 percent higher in the most dense areas compared to the least dense areas. Pedestrian deaths and injuries are most prevalent in urban areas; 72 percent of pedestrian deaths in 2006 occurred in urban settings.

A 1995 Institute study of more than 4,500 crashes in four urban areas found that 22 percent involved drivers who ran red lights or other traffic controls such as stop or yield signs.³ Eighteen percent occurred when a vehicle that was stopped or in the process of stopping was struck from the rear. The three other leading types of urban crashes included running off the road and striking an object (14 percent), swerving into another occupied lane (13 percent), and turning left and colliding with an oncoming vehicle (9 percent). These five crash types accounted for three-fourths of all urban crashes included in the Institute's study and 83 percent of crashes involving injuries.

According to the 1995 Institute study of urban crashes, the risk of injury was greatest in head-on collisions and crashes involving red light running. Occupant injuries occurred in 45 percent of both of these crash types. Forty-one percent of urban crashes associated with a vehicle turning left into oncoming traffic involved injuries. These crashes often involved a side impact. More than a third of the crashes typed as running a traffic control, rear ending a stopped or stopping vehicle, and running off the road involved injury. In contrast, injuries occurred in only 16 percent of crashes involving lane change maneuvers.³

Nearly half of all urban crashes occur at intersections. In 2006, an estimated 1.8 million urban crashes occurred at intersections or were deemed intersection related. Of these intersection crashes, 53 percent occurred at traffic signals; another 21 percent occurred at stop signs. A higher proportion of injury crashes occurred at intersections (50 percent) compared with property-damage-only crashes (42 percent).

Most urban crashes occur in the afternoon or early evening hours. In 2006, 58 percent of urban crashes occurred between noon and 9 pm; another 26 percent occurred between 6 am and noon. While only a small percentage (7 percent) of urban crashes occur between midnight and 6 am, 24 percent of fatal urban crashes occur during these late night/early morning hours.

Pedestrians in urban areas are more likely to be injured in crashes at intersections than at other locations. In 2006, 54 percent of pedestrian crashes in urban areas occurred at intersections. A 1993 examination of fatal pedestrian crashes in four US cities found that 40 percent of the crashes involving vehicles other than large trucks and 51 percent of the crashes involving large trucks occurred at intersections.⁴

Identifying major urban crash types allows city officials to focus on specific ways to prevent future crashes. A 2001 Institute study found that crashes on urban roads often are concentrated at specific locations and occur in patterns that can be reduced through relatively simple and inexpensive engineering modifications.⁵ A subsequent evaluation of low-cost engineering countermeasures implemented at six locations with significant clusters of specific types of crashes found large reductions in the targeted crash types.⁶ At two of the intersections where protected left-turn signals were installed (to permit left turns only when opposing traffic is stopped), left turn crashes were eliminated compared with frequent left turn crashes that occurred prior to the signal changes.

The most common crash type — a driver running a traffic control — might be reduced by lengthening signal clearance intervals, improving signal and sign visibility, increasing sight distances, and reducing vehicle speeds near intersections. A 2002 Institute study of modified yellow and all-red traffic signal timing at urban intersections reported that injury crashes were reduced by 12 percent at experimental sites relative to control sites.⁷ A 2002 Federal Highway Administration study reported that adding left turn and right turn lanes can reduce intersection crashes; the addition of left turn lanes at urban unsignalized intersections reduced crashes by about 30 percent.⁸ Intersection crashes also can be substantially reduced by installing modern roundabouts in place of signals and stop signs. A 2001 Institute study of 23 intersections reported that converting from traffic signals or stop signs to roundabouts reduced injury crashes by 80 percent and all crashes by 40 percent.⁹ At signalized intersections with low traffic volumes, crashes can be reduced by installing multiway stop sign control; a 1997 Institute study reported that multiway stop sign control in place of traffic signals reduced crashes by 24 percent.¹⁰

Common traffic infractions such as speeding and red light running are associated with many urban crashes. Speed cameras and red light cameras can help police enforce traffic laws in dense urban areas where traffic pursuits and stops can be dangerous to officers and to other motorists and pedestrians. Institute research indicates that red light camera enforcement generally reduces violations by 40-50 percent and injury crashes by 25-30 percent.^11,12,13 Drivers in the United States strongly support the use of red light cameras — about 75-80 percent in cities with or without cameras.¹⁴ Speed cameras, used to enforce speed limit laws, have been used only on a limited basis in the United States but are used extensively throughout Europe and in Australia. A 2003 Institute study reported that within 6 months of implementing speed cameras in the District of Columbia in 2001, mean speeds declined by 14 percent and the proportion of vehicles exceeding the speed limit by more than 10 mph declined by 82 percent.¹⁵ An Institute evaluation of fixed speed cameras installed on a busy urban freeway in Scottsdale, Arizona, reported large declines in mean speeds and an 88 percent decrease in the odds of vehicles traveling 11 mph or more above the 65 mph limit.¹⁶ An Institute study of traffic speeds before and after deployment of speed cameras on residential streets in Montgomery County, Maryland, found a 70 percent decline in the proportion of drivers traveling more than 10 mph faster than posted speed limits at locations with both warning signs and speed camera enforcement.¹⁷ The effects of speed cameras on crashes have been the subject of considerable prior research, as summarized in two recent systematic reviews. Pilkington and Kinra (2005) reviewed 14 studies that found various crash reductions in the immediate vicinities of camera sites, ranging from 5 to 69 percent for all crashes, 12 to 65 percent for injury crashes, and 17 to 71 percent for fatal crashes.¹⁸ Wilson et al. (2006) reviewed 21 studies that found reductions ranging from 14 to 72 percent for all crashes, 8 to 46 percent for injury crashes, and 40 to 45 percent for crashes involving fatalities and serious injuries.¹⁹ In addition to speed camera enforcement, consistent police enforcement of safety belt use laws will result in fewer motor vehicle fatalities and injuries resulting from all crash types.

Yes. Many vehicle features available either as optional or standard equipment can reduce urban crashes or their consequences. For example, head restraints are an important safety feature overlooked in many cars. Head restraints can prevent whiplash injuries in relatively minor rear-end crashes, the kind that occur frequently on urban streets. Rear-end collisions account for about 18 percent of all urban crashes, second only to crashes involving running a traffic control.³ A 1999 Institute study found that 26 percent of rear-struck vehicle drivers reported neck injuries.²⁰ Neck injuries, particularly whiplash, occur with significantly higher frequency in rear-end crashes than in other crash configurations. This is why it is important for vehicle head restraints to be well designed to adequately protect occupants. Head restraints should be positioned at least level with the top of the ears, high enough so they are directly behind and very close to the backs of people's heads. A 2003 Institute study compared the rates of insurance claims for driver neck injuries in rear-end crashes before and after seat and head restraint design changes.²¹ A 43 percent reduction in neck injury claim rates was found for Saab, General Motors, and Nissan models with active head restraints, compared with similar models before such restraints were introduced. A 49 percent reduction was found for Volvos equipped with the Whiplash Injury Prevention System, and an 18 percent reduction was found for Fords with improved head restraint geometry. The Toyota Whiplash Injury Lessening system did not show any reduction in neck injuries. A 2008 Institute study examined insurance claims for evidence of driver neck injury for cars and SUVs struck in the rear by the front of another passenger vehicle. Driver neck injury rates were 15 percent lower for vehicles with seats rated good in Institute tests compared with vehicles with seats rated poor.²²

High center-mounted stop lights — a third brake light usually located in a vehicle's rear window — are standard on passenger vehicles. By prominently alerting following drivers that the vehicle in front is braking, the lights have helped reduce the incidence of rear-end collisions by about 5 percent.²³ Another crash avoidance feature is daytime running lights. Activated by the ignition switch, daytime running lights increase vehicle conspicuity during daylight hours, making it easier to detect approaching vehicles. A 2002 Institute study reported a 3 percent decline in daytime multiple-vehicle crash risk in nine US states concurrent with the introduction of daytime running lights.²⁴ Many manufacturers are beginning to make the lights standard on their vehicles.

Good bumpers will not help drivers avoid crashes, but they can reduce repair costs associated with low-speed crashes, which occur frequently on urban streets and in parking lots. An Institute study of vehicles brought to insurance drive-in claims centers in a major metropolitan area during 2001-02 found that about 14 percent of all claims for auto damage involved parking lot collisions — just the kinds of impacts in which strong bumpers could reduce or eliminate much of the damage.²⁵ Yet bumpers are not nearly as damage resistant as they should be because federal requirements for car bumpers are weak, and no requirements apply to the bumpers on pickups, minivans, and SUVs.

Side airbags can reduce serious injuries and deaths in crashes that involve side impacts. About one-fourth of fatal crashes in urban areas involve angle crashes, which often involve side impacts and result in more than 3,000 deaths annually.²⁶ An Institute study found that side airbag designs that include protection for car drivers' heads reduce the risk of driver fatalities in driver-side crashes by 37 percent; airbags that protect the torso but not the head reduce deaths by 26 percent. The death risk for drivers of SUVs involved in driver-side collisions was reduced by 52 percent with head protecting side airbags and by 30 percent with torso-only airbags.²⁷