— Speed -- the No. 1 factor in crashes in Alabama -- and traffic volumes raise the risk of fatal accidents. Where those two elements combine, there are identifiable pockets of higher occurrences, crash data for Jefferson and Shelby counties show.
Between 2007 and 2011, 537 fatal crashes in those two counties killed 590 people, according to the latest complete data from the National Highway Traffic Safety Administration's census of fatal wreck records.
Data show the number of fatal crashes trending upward toward the end of that period, though stronger laws intended to improve driver behavior could reverse the trend, analysts say.
. Interstate 20/59 at Arkadelphia Road: 12 crashes, 13 deaths. Annual average daily traffic figures from 2011 show up to 141,000 vehicles per day along I-20/59; 40,000 along Arkadelphia Road north of the interstate.
. Interstate 65/Interstate 459 interchange: Seven crashes, 10 deaths. Traffic count at the edges of the interchange show 106,000 vehicles per day pass along I-459; 110,000 to 115,000 along I-65.
. Interstate 20/59 between First Avenue North and Roebuck Parkway: Seven crashes, seven deaths. Three were single-vehicle crashes. Traffic ranges from about 55,000 vehicles per day near Roebuck Parkway to about 70,000 near First Avenue.
. U.S. 78 (Forestdale Boulevard) roughly from Cherry Avenue to Dugan Avenue: Six crashes, Six deaths. Two involved pedestrians. Traffic count for that stretch, 40,000 to 45,000 vehicles per day.
. Interstate 65-Interstate 20/59 ("Malfunction Junction") interchange: Six crashes, six deaths. Three were single-vehicle crashes, one involved a pedestrian. Traffic count up to 157,000 vehicles per day along I-20/59 and about 126,000 near the junction.
. Interstate 20/59 at Tallapoosa Street: Five crashes, Five deaths. On average, up to 151,000 vehicles per day pass through that stretch. Tallapoosa Street averaged about 51,000 at the interchange. Three of the crashes involved drivers striking the sides of other vehicles headed in the same direction, data show.
But fatal crashes give only a partial snapshot said Dave Brown, deputy director of the University of Alabama's Center for Advanced Public Safety.
State statistics show there were more than 27,000 non-fatal and fatal crashes reported in Jefferson and Shelby counties in 2011 alone.
Factors such as alcohol and drug use make fatal crashes a random variable, Brown said. Some factors are strong multipliers of fatal crash risk.
Plus, for every 10 mph increase in speed, the chances double of a person dying in a crash, Alabama State Trooper Sgt. Steve Jarrett said.
In 2011, the latest year with the most complete statistics, there were 114 fatal crashes in Jefferson and Shelby County. The 2011 total marked an increase of 22 percent compared with 2009, the lowest point of the five-year time period with only 93 fatal crashes.
Basically, that was caused by the recession and people driving less," Brown said of 2009.
For the five-year period, about 19 percent of the crashes involved drunk drivers, statistics show.
Day by day, more fatal crashes occurred on weekends. The most -- 110 -- happened on Saturdays, followed by 85 on Fridays and 84 on Sundays. Tuesdays had the fewest with 59 recorded crashes.
Breaking the day into four-hour segments, more occurred between midnight and 4 a.m. - 113 -- than any other period, statistics show. There were 98 between 4 p.m. and 8 p.m., the next highest period.
Federal statistics also account for "first harmful events," or what occurred in the crash that led to property damage and deaths.
Trees were involved in about 13 percent of crashes and 10 percent involved pedestrians. Between 2007 and 2011, 55 percent of fatal crashes in the database were single-vehicle wrecks.
Alabama typically ranks higher in traffic fatality rates than other states.
In 2010, the state's traffic fatality rate was 1.34 per 100 million vehicle miles traveled -- an improvement compared to the prior year but still above the nationwide average of 1.11.
Statewide, more crash fatalities occur in rural areas, with factors such as speed, alcohol and response times of emergency rescue coming into play, Brown said.
A growing problem that is difficult to quantify is distracted driving.
Until recently, whether a driver was using some type of electronic device at the time of the crash wasn't recorded, Brown said.
AAA Alabama spokesman Clay Ingram said he expects to see those numbers trend downward in coming years because of two strengthened driver-related laws.
Alabama passed tougher graduated driving laws for teenagers in 2010 and the state's texting-while-driving law went into effect in August 2012.
The graduated laws place new drivers under a veil of restrictions during their first year such as no handheld device use and no nighttime driving -- a high crash-rate period for all drivers.
"I think all those things do make a difference and will help bring those numbers down," Ingram said.
It's a targeted population, but one studies show needs extra enforcement.
The Governors Highway Safety Association's recent survey concluded Alabama teen driver fatalities increased 300 percent during the first six months of 2012 compared with the same period in 2011.
Even with all the technological changes that have made vehicles more able to withstand crashes, Jarrett said proper use of two basic elements can enhance safety: the seat belt and the gas pedal.
Slowing down gives more reaction time to respond to sudden events on the road. State crash statistics in 2011 from the Center for Advanced Public Safety show 60 percent of Alabama drivers who died in crashes were not wearing seat belts.
"If people could see what we see, they would definitely wear a seat belt," Jarrett said.