Addressing work zone safety concerns in Illinois

Evaluating crash characteristics to help identify trends for the development of countermeasures

Juan D. Pava, P.E. / May 04, 2021 / 4 minute read
Illinois work zone crashes and injuries
All images: Illinois DOT

Work zone related fatalities and serious injuries typically account for 2% to 4% and 1% to 2% of all fatalities and serious injuries respectively in Illinois. 

Although these can be considered lower priority areas from a comprehensive strategic approach to safety, work zones are areas where road owners and contractors may have an important and influential role in improving safety. With the goal to deliver better facilities to prevent fatalities and serious injuries, the Illinois Department of Transportation (IDOT) has committed to identifying crash trends, identifying countermeasures and best practices, and implementing and measuring the efficacy of identified countermeasures.

On average, Illinois has experienced over 960 fatal crashes and over 9,140 serious injury crashes per year over the last five years (2015 – 2019). Of those, on average 28.8 (3.0%) fatal crashes and 150.6 (1.6%) serious injury crashes occurred in work zones. Illinois extensively evaluates crash characteristics to identify trends for the development of countermeasures. Vehicle type and crash type were two study areas that generated clear trends that can be addressed to reduce fatalities and serious injuries. 

work zone fatalities

From 2015 to 2019,  8% to 12% of all fatal crashes included heavy vehicle (HV) involvement; these percentages jumped to 20% to 30% in work zone fatal crashes. A similar trend was observed when  reviewing serious injury crashes with the percentage of crashes with heavy vehicle involvement increasing from around 4% in overall crashes to around 10% in work zone crashes. When reviewing the crash type, Illinois focused specifically on the work zone crashes in order to identify types of crashes that are overrepresented and to understand how these crashes fluctuate when heavy vehicles are isolated to determine if these vehicles were more susceptible to a specific type of crash. From 2013 to 2019, the data indicated that over 50% of all work zone fatal crashes could be attributed to front-to-rear crashes (35%) or fixed-object crashes (20%); when reviewing those crashes with heavy vehicle involvement in the same seven-year period, the percentage of front-to-rear crashes jumped to 79%, and was the most prevalent and only significant crash type. When reviewing the serious injury data for the same seven-year period, front-to-rear crashes accounted for 37% of all serious injury work zone crashes and 48% of serious injury work zone crashes with heavy vehicle involvement. Other crash types with significant percentages were fixed-object crashes (13% vs 9%(HV)), turning crashes (14% vs 10%(HV)), and sideswipe-same-direction crashes (6% vs 10%(HV)). 

Illinois has taken a multidisciplinary approach to addressing fatal and serious injury crashes through the Illinois Strategic Highway Safety Plan (IL-SHSP). The IL-SHSP was developed by IDOT with the input and collaboration of stakeholders including Illinois State Police, the Secretary of State, and industry partners including manufacturers, suppliers, contractors, operators, and special interest groups such as bicycle and pedestrian advocates. The overall goal of the IL-SHSP is to eliminate all fatal and serious injury crashes. The plan consists of 14 emphasis areas to aid in the identification and implementation of action items. The emphasis areas are ranked in three priority levels based on the total number of fatal crashes associated with each emphasis area. Heavy vehicles are ranked as a Priority Level 2 emphasis area (8-12% of all fatalities) and work zones are ranked as a Priority Level 3 emphasis area (2-4% of all fatalities).

heavy vehicles

The heavy vehicle emphasis area focuses on addressing safety through improving heavy vehicle inspections, providing training to law enforcement stakeholders on heavy vehicle requirements and licensing, as well as providing education to operators for improved safety behaviors and vehicle maintenance. The work zone emphasis area focuses on the data trends such as the ones presented above to identify and implement countermeasures through engineering, education, and enforcement. IDOT has worked on the identification and implementation of countermeasures to improve traffic flow through work zones, reduce speed differentials, improve positive guidance for road users, increase the use of law enforcement in work zones, and improve education and communication to road users and operators. In the area of enforcement, IDOT has implemented a comprehensive intergovernmental agreement with Illinois State Police allowing the ample use of hire-back officers for work zone specific details including the use of automated speed enforcement, use of police officers for movable back-of-queue warning,  and multi-officer deployments specifically designed to target distracted drivers. 

In the area of education, Illinois works with stakeholders to develop and distribute education and promotional materials to increase the knowledge and awareness of road users of the special constraints in work zones. National Work Zone Awareness Week (NWZAW) is a particularly busy week in Illinois where IDOT and stakeholders work together to engage workers and road users through tailgate talks, media events, and increased social media presence to highlight the identified trends in work zones and provide tips to increase work zone safety. In the area of engineering, IDOT continuously evaluates and improves upon standards, specifications, and policies to enhance work zone safety and mobility. Common practices in Illinois include the design of work zones for the normal posted speed limits instead of the work zone posted speed limits to aid in better mobility through work zones, use of speed display trailers in advance of all lane closures in multilane facilities to increase driver speed compliance, use of transverse temporary rumble strips in advance of lane closures at locations near the expected back of the queue to increase driver awareness of changed conditions, and the implementation of work zone smart systems. The toolbox of countermeasures is continuously evolving, and while many of these countermeasures have been institutionalized, new technologies and approaches continue to emerge as new trends and issues are identified. 

As many of the countermeasures are implemented, Illinois is working on measuring the safety benefits of these countermeasures to help develop best practices guidance and institutionalize their use. Inopportunely, determining the benefit of an individual or combination of countermeasures can be very difficult due to the infrequency and randomness of crashes. However, Illinois was in a downward trend beginning in 2016 and in 2018 and experienced the least number of work zone related fatalities since these numbers were tracked. Unfortunately, the number of fatalities increased in 2019 and preliminary data from 2020 shows the increase was maintained. Illinois reported an increase in number, duration, and length of work zones in 2019 and 2020 which may have had an effect in the overall number of incidents. 

heavy congestion

Since quantifying the benefit of countermeasures implemented statewide is difficult, Illinois was able to realize the safety benefits of countermeasures implemented in a discrete location where after a year of undesirable safety results, changes were made that resulted in a significant reduction of crashes. The work zone in question was an 8-mile interstate rubblization pavement project on I-70 between Altamont and the Little Wabash River in Central Illinois. This location consisted of  a four-lane divided interstate facility with a 22,000 ADT and over 44% HVC.

The project was scheduled to be completed in three construction seasons. Year one, pre-staging work and construction of crossovers took place. Very strict work hour requirements were in place to minimize mobility impacts, daytime lane closures were only allowed between March 1 and May 15. After that date, the contractor was allowed only five additional days for daytime closures. Zero fatalities or serious injuries were reported while work zones were established in year one. Year two, all traffic was placed in a head-to-head configuration on the eastbound lanes separated with a temporary concrete barrier from April 13 to October 29, 2019. A total of 44 crashes were reported resulting in nine injuries and seven fatalities. Review of the crashes suggested the primary cause of crashes was unexpected queuing due to slow moving vehicles along the head-to-head section. In order to address this issue in the short term, the department set up a rest area as an emergency pull-off area and included additional signs to encourage drivers to maintain the work zone speed limit. Year three, all traffic was placed head to head on the westbound lanes, separated by a concrete barrier from April 9 to October 27, 2020. That year, the department set up multiple pull-off areas and included additional signage along the entire head-to-head segment to encourage traffic to continue moving. A total of 25 crashes were reported with only one injury and zero fatalities. This example shows the importance of continuously evaluating the performance of work zones and making changes to address mitigating factors.

work zone safety tips

Traffic-related fatalities continue to be an issue for all transportation professionals, and even though there have been continual efforts to develop and deliver safety solutions, nationwide fatality and serious injury numbers do not seem to be decreasing. Although over 90% of all fatal crashes can be attributed to behavior-related causes, it is the duty of transportation professionals to evaluate how facilities can be more forgiving to allow for driver errors to not result in fatal incidents. This is even more important  in areas such as work zones where all of us—transportation officials, contractors, and other industry partners—can make a significant and lasting impact. It is within our power to make this year the best year. Work safe. Drive safe. Save lives.

About the Author

Pava is Safety Programs Unit Chief with the Bureau of Safety Programs and Engineering (BSPE) at the Illinois Department of Transportation.

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