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Why Did We Examine the Role of Seasonal Factors in Crashes?

We conducted this study to learn more about one factor in particular that frequently arises in our firm’s auto accident investigations: Weather. Of course, weather conditions change as the seasons change. So, we chose to take a closer look at seasonal data from the National Highway Traffic Safety Administration’s Fatality Analysis Reporting System (FARS) in order to determine whether weather conditions during certain seasons may make crashes more likely. We limited the scope of our study to fatal car accidents within a three-year period, 2012 to 2014.”

Our findings surprised us. They might surprise you, too.

Major differences during each season

  • Months: December - February
  • Dangerous Conditions: Snow, ice, sleet, freezing rain
  • Major Holidays/Events: Christmas, New Year, Super Bowl
  • Drivers in Fatal Crashes: 445 total (148 per month)
  • Months: March - May
  • Dangerous Conditions: Fog, high winds, rainstorms
  • Major Holidays/Events: St. Patrick’s Day, Memorial Day
  • Drivers in Fatal Crashes: 451 total (150 per month)
  • Months: June - August
  • Dangerous Conditions: Thunderstorms, heat, humidity
  • Major Holidays/Events: Fourth of July, Labor Day
  • Drivers in Fatal Crashes: 741 total (247 per month)
  • Months: September - November
  • Dangerous Conditions: Fog, frost, late-season snow and ice
  • Major Holidays/Events: Halloween, Thanksgiving
  • Drivers in Fatal Crashes: 645 total (215 per month)

Seasonal factors & statistics

How Does Weather Impact Traffic Safety?

Before we discuss our findings, we should note that numerous studies have examined the influence of the weather on traffic safety.

For instance, the Federal Highway Administration (FHA) recently analyzed crash data between 2004 and 2013 and found that 22 percent of vehicle crashes, 19 percent of crash injuries and 16 percent of crash fatalities each year in the U.S. are “weather-related.” In other words, these crashes occur in “in the presence of adverse weather and/or slick pavement conditions.”

Number of Drivers Who Were Affected by the Weather

Another study by Dutch researchers explained the ways in which adverse weather conditions can affect road safety. As the study noted:

  • Precipitation (rain, snow, hail) – Reduces drivers’ visibility, reduces a car’s “grip” on the road and cuts down on visibility.
  • Fog – Decreases visibility and road friction, possibly causing a car to “hydroplane.”
  • Wind – Pushes vehicles around, especially those with high centers of gravity such as buses, vans, trucks and certain sport-utility vehicles (SUVs).
  • Ice, sleet and slush – Reduces friction and makes roads slippery (including “black ice,” or ice that forms when snow melts and freezes again).
  • Temperature – Heat makes drivers irritable and fatigued and impacts concentration. Cold temperature can impact vehicle performance.

With this in mind, let’s turn to what we found from our examination of Wisconsin fatal crash data.

Winter May Not Be As Dangerous As You Think

Because weather-related driving conditions in Wisconsin appear to be at their worst during the winter, we expected to find the highest number of fatal traffic crashes during the months of December, January and February.

We were wrong: Out of the four seasons, winter actually had the lowest number of drivers involved in fatal crashes with 445.

Additionally, the total drivers in fatal crashes during “winter weather” such as snow, sleet and freezing rain came out to 176, or only 7.7 percent of the 2,282 drivers in fatal accidents.

During the summer months of June, July and August – in terms of weather conditions, the most ideal time of the year in our state – the highest number of drivers were involved in fatal crashes with 741.

Autumn (September, October and November) had the second-highest tally with 645, while spring (March, April and May) had the third-highest count with 451.

Does This Mean Winter Is A Safe Time of Year on Wisconsin Roads?

One may be tempted to look at these numbers and conclude that there is nothing more dangerous about driving in Wisconsin during the winter than at other times of the year. In fact, one could even find that, the better driving conditions are, the more dangerous our roads become.

However, we believe one should take two factors into consideration, which may help to explain the lower winter fatality counts:

  • Speed – As Wisconsin Department of Transportation (WisDOT) data shows, excessive speed is one of the leading causes of fatal crashes in our state. However, when road conditions become icy and snowy during the winter, people tend to drive slower. As a result, the number of total crashes may still be fairly high – WisDOT reports that, on average, 18,000 crashes occur each year during the winter months – but they may occur at slower, less deadly speeds than they do at other times of the year.
  • Traffic – When inclement weather hits our region during the winter, people simply tend to stay off the roads as much as possible. Lower traffic naturally leads to a lower number of fatalities. In contrast, traffic in Wisconsin tends to pick up heavily during the summer months as conditions improve and daylight increases, resulting in a spike in fatal crashes.

In other words, looking at the weather – in isolation – may not always explain why crashes tend to happen in Wisconsin. One needs to look at other factors and address those when seeking ways to reduce the number of fatal traffic accidents on our roads.

Does Daylight Savings Time Affect Fatal Crashes?

As our review of the FARS data revealed, when daylight savings time ends and begins may be a significant factor in crashes. Wisconsin drivers tend to have a tough time adjusting to the time changes. Between 2012 and 2014, the number of drivers who died in crashes during the week before a time change to the number who died in the week after the change increased from 54 to 81, or by 50 percent.

When Daylight Savings Ends

The transition to nighttime driving proved to be more difficult for Wisconsin drivers than the transition to daylight driving. For instance, when daylight savings time ends in the autumn – you turn back your clock one hour, or “fall back” – drivers find themselves making their evening commute at dusk or in the dark.

The FARS data from 2012 to 2014 shows that the total number of drivers involved in fatal crashes in Wisconsin during that period went from 29 during the week before daylight savings time ended to 49 in the week after it ended, or an increase of 69 percent.

It is also important to note that more drivers died during the three-year period in crashes that occurred at dusk (62) than at dawn (41).

Week Before Week After
29 49

When Daylight Savings Begins

In contrast, the beginning of daylight savings time – when you set your clock ahead one hour, or “spring forward” – proved to be less dangerous, based on the FARS data. The beginning of daylight savings time marks the return of more sunlight during one’s evening commute.

During the time period we studied, the total number of drivers involved in fatal crashes in Wisconsin went from 25 during the week before daylight savings time began to 32 during the week after, or an increase of only 28 percent.

Week Before Week After
25 32

What Can We Learn from Our Seasonal Driving Study?

While promoting traffic safety should be a year-round project, our analysis of the FARS data revealed that the summer season – rather than winter – may be the time of year to target unsafe driving practices that lead to accidents.

While summer may be a better time of year to be on our roads in terms of weather conditions, the combination of high speeds and a high volume of traffic in the summer can prove to be dangerous.

As the summer begins, it can be the ideal time to raise drivers’ awareness of the risks created by not only speeding but drinking and driving, driving while fatigued and driving while distracted by phones or passengers as well.

Additionally, our analysis indicates that more should be done to warn drivers about the impact that time changes can have on their driving, especially when daylight savings time ends. For instance, we can make efforts to educate drivers about problems that can arise when driving in low-light conditions such as dusk.

Why Did We Conduct This Wisconsin Car Accident Study?

Gruber Law Offices, LLC, is a Wisconsin personal injury law firm headquartered in Milwaukee, WI. A major focus of our practice is the representation of auto accident victims and their families. Due to this focus, our firm is always interested in learning more about factors that contribute to crashes in our state. Knowing more about these factors, we believe, plays a vital role in the prevention of these often tragic events.