Improving Safety in the Work Zone

by Courtney Murtagh, Intern, and Tracy Zafian, Research Fellow

In 2015, 860 vehicle crashes in roadway work zones were reported in Massachusetts, and over 96,000 crashes in work zones nationwide. Researchers and state officials have been examining the causes, and options for reducing work zone crashes, injuries, and fatalities.

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Work zone area on the MassPike during the removal of toll booths. (Boston Herald, photo credit Angela Rowlings)

With summer in full swing, we find ourselves in the midst of another road infrastructure improvement and repair season. Drivers may have noticed an increase in the number of work zones along state and town highways in Massachusetts. During these warmer months, drivers need to take extra precautions for their safety and the safety of road construction workers.

The Federal Highway Administration (FHWA) recorded a total of 765 work zone traffic fatalities nationwide in 2016, in the Fatality Analysis and Recording System (FARS). This is a 7% increase from 2015.  Many of these fatalities (83%) were of motor vehicle drivers or passengers, the remainder were pedestrians, bicyclists, and other non-motorists. Relatedly, the U.S. Bureau of Labor Statistics found that there were 143 deaths of road workers at construction sites. This count overlaps with the FARS figures. Forty percent of the traffic fatalities in work zones are from rear-end collisions, as vehicles fail to slow down adequately approaching and traveling through the work zones.

According to the FHWA, there were 96,626 crashes in work zones in 2015, a 42% increase since 2013. The same study showed that nationwide there were on average 70 work zone traffic crashes with injury per day that year.

For Massachusetts, the State Police reported 860 work zone crashes for 2015. The data show that work zone crashes occur most often between May and September, during the day, and on a Tuesday, Wednesday or Thursday. Drivers should be especially cautious and attentive when traveling through work zones, as construction workers may be present and as drivers may be asked to stop.

Speed limits in work zones are set according to state law. The law allows for the doubling of speeding fines in work zone areas.

In 2016, MassDOT created a Work Zone Safety Task Force to consider innovative engineering and technology-related solutions for better work zone safety. The Work Zone Task Force implemented some new safety features in work zones in 2017, including portable rumble strips, and flashing blue LED lights in work zones to simulate a police presence and get drivers to reduce their speed. Another type of technology being considered are smart cones, which communicate with construction workers to warn them when potential threats, such as a speeding or erratically driving vehicle, are approaching a work zone. A previous Innovative Outlook article discussed some of the technology options for improved work zone safety in more detail.

Another potential way to reduce work zone crashes is the ‘zipper’ merge. The zipper occurs when two lanes of traffic equally merge into one. Research conducted at UMass Amherst by Dr. Michael Knodler and Civil Engineering graduate students Alyssa Ryan and Francis Tainter has been investigating the potential use of zipper merges to help improve traffic safety. UMass Amherst’s zipper merge research was discussed in the March and April 2018 Innovative Outlook. An FHWA analysis of FARS crash fatality data found improper merging to be the second most dangerous driving maneuver, behind only inattentive driving. The zipper merge is hypothesized to improve both roadway safety and efficiency, including in work zone areas.

Around and Around for Pedestrian and Cyclist Safety

by Tracy Zafian, Research Fellow, and Courtney Murtagh, UMTC Intern

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Bicycle in Roundabout (Source: bikewalkencinitas.org)

Roundabouts were introduced to America’s traffic system as a way to increase traffic safety and support greater traffic volumes without extensive new construction. A roundabout’s circular formation works by making incoming vehicles yield to circulating and exiting traffic. This allows cars to maintain a steady traffic flow through the intersection and not have to come to a complete stop. Roundabouts have been proven to be able to handle up to 50 percent more traffic compared to traditional intersections that use traffic signals or stop signs. Further, due to vehicles’ reduced speeds at roundabouts, crash and injury rates can significantly decrease, especially for motorists. According to the Insurance Institute on Highway Safety (IIHS), studies of U.S. intersections that have switched from stop signs or traffic signals to roundabouts have found a decrease in all traffic crashes of 35-47% and a reduction of injury crashes of 72-80%. The IIHS importantly notes that the U.S. studies have focused primarily on single-lane roundabouts. When included in research studies, two-lane roundabouts have been shown to have smaller reductions in crashes compared with single-lane roundabouts or even with increases in crashes. Crashes at roundabouts have also involved bicycle and pedestrians. Non-motorized road users, such as bicyclists and pedestrians, can face several safety and technical challenges when traveling through roundabouts. These challenges can lead to greater crash risk at roundabouts.  Dr. Eleni Christofa, UMTC Affiliate Researcher Civil Engineering and Professor Aura Ganz of Electric and Computer Engineering from UMass Amherst are studying the safety of visually impaired pedestrians at roundabouts. Visually impaired pedestrians may be used to having auditory cues from traffic and signals at intersections to know when it’s safe to cross. Roundabouts, designed with continuous traffic flow in mind, may not have such cues. Additionally, it can be difficult for drivers to detect pedestrians at a crosswalk while the driver is focused on navigating a roundabout.  Dr. Christofa and Dr. Ganz have developed a new dynamic warning sign to alert drivers entering a roundabout as to where pedestrians are attempting to cross. This sign contains a symbolic traffic circle and symbolic crosswalks for each approach of the roundabout. If a pedestrian is about to cross one of the roundabout’s approaches, they can activate the sign which will then flash to alert drivers where pedestrians are crossing in the roundabout. This is designed to help both with driver awareness of pedestrians and pedestrian safety. The dynamic warning sign will be tested on the UMass Amherst advanced driving simulator this summer. If the sign works as expected, it could be used to help with the safety of pedestrians at roundabouts generally and particularly for the visually impaired and those with mobility impairments who take longer in crosswalks.

 

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Proposed dynamic warning sign for pedestrian crossings at roundabouts. Pedestrians activate the sign to flash and show where they are crossing to help alert drivers traversing the roundabout to their presence.

One of Dr. Christofa’ s graduate students, Derek Roach, conducted other research on roundabouts for his Master’s thesis. His study looked at the impact of roundabouts from a driver behavior, vehicle emissions, and safety perspective. As part of his research, Roach reviewed other studies that examined the safety of bicyclists and pedestrians at roundabouts. One of these studies found that drivers who are exiting a roundabout are less likely to yield to pedestrians than when the drivers enter the roundabout.  This same study found that as speed increases in roundabouts, drivers are less likely to yield for pedestrians, making it harder and less safe for pedestrians to cross.

In terms of bicyclist safety, Roach examined a number of studies by researcher Stijn Daniels and colleagues in Belgium. Daniels’ work has found increases in the number of bicyclist crashes and in crash severity when intersections are replaced with roundabouts. Other studies have reported potential explanations for these increases. One study, by researcher Bob Cumming in Australia, found that a contributing factor of bicyclist crashes in one lane roundabouts was bicyclists staying very close to the right curb while going through the roundabout, which would lead motorists to try and pass them in the roundabout. In these cases, it is safer for bicyclists to take the main travel lane instead of being so close to the curb.

At the MassDOT’s 2017 Innovation and Tech Transfer Exchange, presenters from Kittelson and Associates gave an overview on bicycles at roundabouts, including a review of bicycle facility design standards and practices in Massachusetts and elsewhere. Each of the MassDOT Highway Districts in the state has at least one roundabout. MassDOT’s guidance for roundabouts gives special attention to rotary retrofits, building roundabouts in constrained environments, and incorporating state-of-the-practice bicycle and pedestrian design into roundabouts. One important current practice is to treat low-traffic volume and high-traffic volume roundabouts differently, to support bicyclist safety. For lower traffic roundabouts, bicycles are encouraged to circulate with motor vehicles. For higher traffic roundabouts, it is encouraged for bicycles to have a protected intersection with a separate bicycle path, and for bicyclists to have the option of either going through the intersection as a vehicle or pedestrian.

Hot Mix Asphalt Mixtures – What Works

by Courtney Murtagh, UMTC Intern, and Tracy Zafian, Research Fellow

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Road paving project in Lee, MA, 2010. (Source: blog.mass.gov).

Dr. Walaa Mogawer, UMTC Research Affiliate, Professor at UMass-Dartmouth, and UMass-Dartmouth Research Engineer Alexander Austerman recently published the results of their research study on Experimental Hot Mix Asphalt Projects Placed in Massachusetts. Professor Mogawer discussed this research topic in an Innovative Outlook interview in September 2017.

The study’s primary goal was to monitor roadway projects in the Commonwealth that used different experimental mixtures of asphalt to see which mixtures worked best, with the longest service life, best distress resistance, and easiest placement or construction. As described in the study report, the data gathered through this study can aid “Massachusetts in determining if full-scale implementation of these design methodologies and technologies is cost-effective in the long term. Overall, it is anticipated that well-performing technologies could be separated from poor-performing ones, thus leading to better decisions for future infrastructure.”

This study, conducted over a 5-year period (2012-2017), evaluated the performance of experimental hot mix asphalt (HMA) mixtures used in 12 different road pavement projects around Massachusetts. The 12 projects selected by MassDOT staff for this evaluation each involved new pavement technologies or new specifications. These technologies and specifications were tried for a variety of reasons, ranging from trying to mitigate reflective cracks in HMA layers placed over plain concrete slabs to the construction of environmentally friendly “green roads” by the incorporation of warm mix asphalt and ground tire rubber.

As described in the report, at the start of the study the researchers worked to collect all available data from MassDOT on each of the selected projects, including “all bid contract documents, material specifications, plant reports, construction quality assurance data, ride quality and distress data.”

The study then involved developing monitoring plans for each selected project, some of which had been constructed prior to the study. For each site, condition data were collected periodically throughout the duration of the study to quantify the performance of each mix and the changes in performance over time. Data were collected in the same manner for each project, using standardized techniques from MassDOT’s Pavement Management Section, such as surveying distress and calculating the relevant Pavement Condition Index (PCI). This ensured fair and consistent measurements and evaluations for each site.

The study’s primary conclusions and recommendations were as follows:

  • The condition data provided by the MassDOT Pavement Management Section provided critical data required to be able to evaluate the performance of monitored projects over an extended period of time.
  • The tested alternative technologies and specifications generally provided acceptable performance in terms of rutting, cracking and ride quality. If the projects continue to display acceptable levels of performance over time, it was suggested that final specifications be developed so that that same mixtures and strategies can be used in the future.
  • For future road paving projects involving new technologies, it was recommended that a monitoring plan be developed and implemented before the start of these projects. This would allow for a more comprehensive collection of data regarding the technologies’ performance and cost-benefit results over time and assist MassDOT in making more informed decisions when developing project specifications.

The final study report by Dr. Mogawer and Mr. Austerman can be viewed at this link.  This research was funded through the MassDOT Research Program with Federal Highway Administration (FHWA) State Planning and Research (SPR) funds.

Zipper UP – Merge Design Helps Reduce Crashes

by: Tracy Zafian, Research Fellow

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Texas DOT blog

A recent study from the University of Massachusetts (UMass) Amherst evaluated the impact of various merge signs and road geometries on driver perception and behavior at merges.  Alyssa Ryan, a UMass Amherst Transportation Engineering graduate student working with Dr. Michael Knodler presented findings of the “Alternative Merge Design Downstream of Intersections,” focused on alternative merges, also known as zipper merges.  The study was discussed at the Road Safety and Simulation Conference in the Netherlands in October; additional results were presented at the annual meeting of the Transportation Research Board in Washington, D.C. in January. Discussing the importance of this research, Dr. Knodler said, “If we are able to change driver behavior to better promote alternate merging, we have the potential to improve both roadway safety and efficiency.”

The zipper merges occur when two lanes of traffic equally merge into one, rather than a standard merge from the right lane to the left, or left to right. Ideally, for zipper merges, similar levels of traffic occupy the left and right lanes approaching the merge, and then the vehicles merge into the single lane alternating from the left lane and then the right lane, vehicle by vehicle, as in the two sides of a zipper coming together. A demonstration video of a zipper merge by the Alberta Motor Association can be seen here. The UMass Amherst researchers hypothesized that “by changing signage from the traditional “Lanes End Sign” to experimental signs that promote alternative merging, drivers will be more likely to merge evenly downstream” of the lane drop location…. Even merging will present a greater balance in lane utilization, which will lead to reduced congestion and potentially improved safety.”

Traffic merges can create challenging situations for drivers and safety. The Highway Safety and Information System (HSIS), a multi-state database of a crash, traffic volume, and roadway inventory data, includes information on the driving maneuvers that result in the most truck and car crashes. In an examination of HSIS crash data for twenty-six driving maneuvers, improper merges were listed as the second most dangerous, behind inattentive driving.

The current standard traffic sign used to let drivers know that they are approaching a merge is the W4-2 sign, also known as the “Lane Ends” sign, defined in the Manual on Uniform Traffic Control Devices (MUTCD). This is the first sign on the left in the chart below. With this sign, there is no indication of how the vehicles should merge into one lane, and it also appears that the right-lane traffic will yield to traffic on the left, which is a different merging approach that is used with the zipper merge.

The UMass study had two main components. The first involved a survey of drivers regarding different potential merge signs. Drivers were shown pictures of different signs and different road-perspective views of merging road lanes. The survey asked them questions such as “In the lane drop pictured, a merge is required. With the given sign below, which lane do you prefer to approach the lane drop in?” Drivers were also shown road pictures and asked: “Knowing that you will be merging ahead, as shown, which sign would you prefer to promote EVEN MERGING?”  The different signs shown to the survey participants are in the figure here. Aside from the W4-2 sign, each of the other signs has been used in signage studies before, either at the Federal Highway Administration (FHWA)’s Human Factors Laboratory or for a study conducted in Connecticut.

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Participant Sign Preference to Encourage Even Merging

 

The study found that with the traditional “Lanes Ends” sign, or with no sign before the merge, most survey participants indicated that they would prefer to stay in the left lane approaching the merge. With the other no-text sign options, between 30-40% of participants indicated that they had no preference between the left and right lane approaching the merge. With each of the text sign options, participants showed a preference for staying in the left lane approaching the merge though the percentages selecting the left lane or indicating no preference was almost equal for the “Alternative Merge” sign.

On the question of which sign(s) participants thought would best promote even merging, the “Lane Ends” sign was the least preferred. The “Alternative Merge” sign was the most preferred of the 8 sign options, for promoting even merging. At the same time, however, one in five (20%) of the survey respondents also rated it the least preferred.

The second part of the UMass study involved testing the most preferred signs for even merging on the UMass-Amherst advanced driving simulator. This allowed the research team to validate whether the stated preferences from the survey would match drivers’ lane choices in merge scenarios in a driving simulation environment. The preliminary results of the simulator study will be discussed more in April’s Innovative Outlook.

The findings of this research may be helpful on roadways with alternative merge configurations, either more permanent or in work zone areas where one lane is closed on a temporary basis.

For more information on this study, you can contact Alyssa Ryan by email at alyssaryan@umass.edu.

Pedestrian Research Findings Presented to MassDOT

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Belmont Ave., Holyoke, MA

On Friday, Jan 26th, Dr. Robert Ryan, from UMass Amherst, and his graduate students presented their results on The Role of Street Trees on Pedestrian Safety research project at an Executive Briefing meeting which took place in the Office of Transportation Planning (OTP).  This research aims to study the link between street trees and pedestrians’ perceptions of safety, along with actual safety while walking along street corridors in Chicopee, Holyoke and Springfield.

One research objective for this project centers on how road volume across street corridors, as well as streetscape features may impact pedestrian safety. Another key objective includes understanding how both residents and nonresidents value the presence or absence of street trees as related to vehicular traffic speed, as well as how to spatially assess pedestrian-vehicle accident reports with the presence of street trees.

Preliminary findings discussed at the Executive Briefing include:

  • Socio-demographic information
  • Important features for walking route choice
  • Results by city
  • Results by street tree cover
  • Results by age, gender, income, and race
  • Preference for additional tree plantings and future improvements

MassDOT at TRB 2018!

by: Matt Mann, Research Program Coordinator

Image result for transportation infrastructure repurposing

Nikki Tishler, Transportation Planner and Title VI Strategist for MassDOT, provided great moderating skills at last week’s Transportation Research Board Annual Conference, as she orchestrated the session: Repurposing and Resizing Our Infrastructure: Responsible Investment for the New World.  The presentations and discussions centered on right-sizing the infrastructure for future transportation function, efficiency and service.  DOT’s continue to improve project and asset management processes as they integrate existing and future societal needs with an anticipated reduction in funding.