Zipper UP – Merge Design Helps Reduce Crashes

by: Tracy Zafian, Research Fellow

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.

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

Drunk Driving…Continues to be a Major Concern

by Tracy Zafian, Research Fellow

from: White & Associates Law, MN

A bold new report leads with that statement and recommends a multi-faceted, comprehensive approach to eliminating drunk-driving related deaths. The report comes from the Committee on Accelerating Progress to Reduce Alcohol-Impaired Driving Fatalities, a committee convened by the National Academy of Sciences, Engineering, and Medicine to address this topic. The committee supports the concept of Vision Zero, stating in their report that “no alcohol-impaired driving deaths are acceptable, and that every stakeholder has a role in preventing these deaths.”

“Alcohol-impaired driving remains the deadliest and costliest danger on U.S. roads today.  Every day in the U.S., 29 people die in an alcohol-impaired driving crash – one death every 49 minutes – making it a persistent public health and safety problem.”

The report documents how, beginning in the 1980s, steps were taken to reduce drunk driving and to educate the public about its dangers. Such steps included new laws making it illegal to drive with a blood alcohol concentration (BAC) level above a certain level. These approaches lead to a decrease in drunk driving-related fatalities for two decades, but now the decline in these fatalities has plateaued. It is clear that a new approach is needed for progress to continue.

The committee created a conceptual framework to show the sequence of behaviors that can lead to an alcohol-impaired driving fatality, potential interventions for this behavior, and important factors that impact outcomes. The interventions would interact with each other at multiple levels, including “individual, interpersonal, institutional, community, and societal.”

The interventions fall into four primary categories:

  • Interventions to reduce drinking to impairment, such as limiting alcohol availability and marketing, especially for under-age drinkers
  • Interventions to reduce driving while impaired, including: creating viable, affordable, safe transportation alternatives for drinkers who may drive; strongly enforcing drunk driving laws; and promoting the use in-vehicle technologies that can restrict drivers with over a threshold BAC level from being able to start their vehicle.
  • Post-arrest and post-crash interventions, such as health care programs for preventing, evaluating, and treating alcohol dependency; and increased support both for first-time driving under the influence (DUI) offenders as well as habitual offenders to modify these behaviors.
  • Data and surveillance systems, including: expanding and standardizing data collection on alcohol-impaired related crashes, arrests, and convictions, long-term outcomes, and why people drive while impaired; and integrating the collected data sets for research, evaluation, and data-sharing purposes.

 Massachusetts has a history of addressing the issue of alcohol-impaired driving using education and enforcement with the coordination of multiple agencies. Each year for example, the state Executive Office of Public Safety and Security leads the Drive Sober or Get Pulled Over enforcement and education effort over the December-New Year holiday season.  This effort includes high visibility police patrols and impaired driving enforcement at high crash locations across the state. One result of Massachusetts’ efforts is that the rate of alcohol-impaired traffic deaths in Massachusetts is consistently among the lowest in the nation. Moreover, the rate of alcohol-related driving deaths in Massachusetts has fallen approximately 20 percent since 2007. However, as with the national trends, the decrease in these deaths in Massachusetts has slowed in recent years, and between 2015 and 2016, there was actually a small increase from 109 to 119 people killed statewide in alcohol-related crashes.

Keeping Skies Safe with Drones

by: Michael Plotnikov, Research Fellow

Integration of unmanned aircraft into our national airspace poses complex security challenges that regulatory agencies may not be entirely prepared to face. While the Federal Aviation Administration (FAA) has done an excellent job preserving safety in the national airspace, no comprehensive effort has been made to protect critical infrastructure from the air, or to determine how to prevent unmanned aircraft from being hacked and used for malicious purposes.

Unmanned aircraft in the form of radio controlled model aircraft have been around for many years. However, with the addition of innovations such as on-board processors, GPS receivers, cameras, and other sensors, this old technology has evolved into a cyber-physical system that has both expanded capabilities and vulnerabilities.

While new capabilities of unmanned aircraft systems (UASs) are well-known, their vulnerabilities, especially related to hacking through communication links, navigation equipment, and malicious software are not well understood. In addition, vulnerabilities of critical infrastructure, particularly ground transportation to malicious UAS attacks should be thoroughly evaluated:

  • First, it is extremely important that technical measures be taken to prevent non-cooperative UASs from penetrating restricted areas by means of reliable detection, tracking, and deterrence. While most of the high-profile infrastructure objects are well-protected or difficult to access at the ground level, they are usually completely exposed to attacks from the sky. The increasing availability of small UAS and their greatly improved capabilities over recent years makes this vulnerability particularly dangerous.
  • Second, technical steps need to be implemented to ensure that wireless communication links used to guide and control unmanned aircraft are secure and cannot be hacked or jammed by hackers who intend to take over control of the aircraft. While the incidence of such successful hacks may indeed be less common, in relation to the general availability of UAS technology to a malicious party, hacking may be particularly dangerous as adversaries get access to a vehicle that is authorized to enter a restricted area and hence may not trigger a timely alarm as would be the case when entry occurs under the malicious control.

Two recent MassDOT research publications address the practices of drones and the impacts of drones around airports: The Practice of UAS in the Transportation System, developed by Research Affiliates Daiheng Ni and Michael Plotnikov, and Current Counter-Drone Technology Solutions to Shield Airports and Approach and Departure Corridors developed by Research Affiliates  Douglas Looze, Michael Plotnikov and Ryan Wicks.  Additional research is needed to determine what cyber-security based systems are available to preserve UAS security and prevent UAS hacking and cyber-attacks as well as what technologies are available to enable timely detection and tracking of unauthorized UASs. To this end, an initial step that should be taken is to conduct a study to determine the costs, capabilities, and limitations of readily available commercial-off-the-shelf (COTS) cyber-security systems. From this, Jeff DiCarlo, Project Champion, MassDOT, will soon be kicking off The Application of Unmanned Aerial Systems (UAS) in Surface Transportation project.

Are Your Lights Iced?

by: Tracy Zafian, Research Fellow

Image result for train rail flashing lights

Many highway and rail signals now contain Light Emitting Diodes (LEDs). The switch to LEDs was made because of its energy efficiency. However, a one side-effect of this efficiency is that the LED lights don’t give off enough heat to melt snow or ice on their own. This can lead to the lights being obscured during winter conditions which can create potential safety hazards. In 2016, for example, there was a crash in Windsor, Ontario where a school bus entered an intersection against a red light and ran into a car. The bus driver did not see the red light-an LED, because the light was obscured by snow. Fortunately, there were no major injuries during that crash. Early this winter, the Minnesota DOT worked to clean off LED traffic signals after snow obscured signals in the Twin Cities area of the MN Highway 36, leading to at least one serious crash and many near misses.

In 2014, the Federal Highway Administration (FHWA) released a report on LED traffic signal operations in snow conditions which suggested a number of proactive and reactive measures transportation departments can take to keep LED signal lights free from ice and snow. Reactive measures, employed after a snowfall, include manually cleaning the lights or spraying them with antifreeze, deicing spray or compressed air to clean them off. Each of these measures requires personnel to visit and work on each light. Proactive measures include installing signal lens heating elements or lens covers, or spraying deicing spray on the lights before it snows. As documented in the report, such proactive measures have had various degrees of success.

Two current research studies are testing new proactive approaches, both of which involve redesigning the LEDs lights used in traffic signals. Researchers at the University of Kansas have developed and tested self-de-icing LED technology and are now working on creating a full prototype for field testing. . Their approach is to mount the LEDs in the traffic signals “backwards” to harvest the heat generated by the LEDs to heat the light lenses and keep them above freezing. With this system, no additional heating is needed to prevent ice and snow from collecting on the traffic lights. The researchers have estimated that replacing the current LED lights with new LEDs will save about $28 per signal light annually, with a payback time of 4.5 years.

A second research study is looking at developing a super hydrophobic (anti-icing) surface coating for the lenses of traffic signals. The research is being conducted at the University of Nebraska, Lincoln, and is investigating femtosecond laser surface processing (FLSP) techniques for producing thin (nanoscale) anti-wetting surfaces on hard materials, such as tungsten carbide. Testing is being conducted find the best FLSP-functionalized hard material to use as a durable stamp for imprinting an anti-icing surface on the lenses of traffic signals. This study is scheduled to be completed later this year.

Mom, I missed the bus… you didn’t

by Matt Mann, Research Program Coordinator


Chilly mornings can be dangerous to kids that wait for the school bus.  Until now, parents and students just assumed that if they weren’t at the bus stop in time, they had missed the bus.  Now there’s an app that tracks the location of the school bus and can also track when a child has boarded the bus and when they have gotten off.

The ‘Here Comes the Bus’ app is currently being discussed by many more School Boards.  This locator would prevent kids from waiting out in the elements for the bus that could have come early or might be delayed.  This app would provide parents and kids the location of the bus and allow them to meet it just as it arrives at the bus stop.

Another feature, which is optional, is the app can also alert parents when their child has gotten on and off the bus; assuring that they got on the right bus and that they are en-route.  This feature is up to the school boards to decide if they want it.

New Federal Committee on Motorcycle Safety Holds First Meeting

by Tracy Zafian, Research Fellow


Last month, the Motorcycle Advisory Committee (MAC) held its initial meeting in Arlington, VA. This federal committee was created to advise the Federal Highway Administration (FHWA) on motorcycle safety and to identify engineering-related infrastructure solutions for reducing motorcyclist fatalities.

There were 5,286 roadway fatalities nationally involving motorcycles in 2016, an increase of 5% from the previous year. In Massachusetts, 40 motorcyclist fatalities were reported during the same year.

As described on, “the MAC consists of ten members selected by the U.S. Secretary of Transportation Elaine L. Chao. [The members] come from across the country and are experts in a wide range of motorcycle-infrastructure topics. Each is a motorcyclist and, combined, the MAC members have over two centuries of riding experience.”

At the first MAC meeting, there were substantial discussions on many infrastructure issues, including work zones, roundabouts, roadside hardware, roadway maintenance practices, the potential consequences of automated vehicles and crash testing, among others. At upcoming meetings, the MAC will determine how to advise FHWA on these issues. For its part, FHWA has research underway to identify key infrastructure-based safety issues for motorcyclists. The centerpiece of this work is the FHWA’s Motorcycle Crash Causation Study. According to the study web site, “The Motorcycle Crash Causation Study is the most comprehensive data collection effort to study the causes of U.S. motorcycle crashes in more than 30 years. The dataset includes data from at least 351 crash investigations, and 702 control rider interviews.”

A couple of current safety features on motorcycles to prevent future fatalities include: new breaking lights and the required anti-lock brake feature. The break light feature is the first wearable brake light connected to a smart phone app.  The anti-lock brake feature has been an option on motorcycles for years, but it may soon become a requirement based on the safety advantages.

In addition to technology and infrastructure improvements for motorcycle safety, some changes in how motorcyclists are trained may be warranted as well. Researchers at UMass-Amherst, led by now Ph.D. graduate Jeffrey Muttart, have conducted field studies on motorcyclist eye glance and driving behavior, including studies where participants went through the same on-road course as car drivers and as motorcyclists. Key findings in one study were that motorcyclists were less likely to come to a complete stop at a stop sign than car drivers, and that study participants made later final glances toward the direction of the most threatening traffic before they made a turn when they were driving a car than when they were riding a motorcycle.

Rectangular Rapid Flashing Beacon Devices Rescinded

by: Matt Mann, Research Program Coordinator

A Rectangular Rapid Flash Beacon (RRFB). Source: Carol Kachadoorian (2012)

Many Massachusetts towns and educational institutions, like UMass Amherst, have installed Rectangular Rapid Flashing Beacon (RRFB) devices at crosswalks, to alert drivers of a pedestrian crossing. This will be changing in the future. The Manual on Uniform Traffic Control Devices (MUTCD) prohibits patented devices from experimentation, Interim Approval (IA), or inclusion in the MUTCD. Based on an Interim Approval, in June 2008, for this device, the US Department of Transportation, Federal Highway Division recently rescinded all new RRFB devices. Existing devices, already installed, can remain in-place for their useful life.  Additional information will be forth coming.  Please contact FHWA Massachusetts division office for guidance.

New Year, New UMass Human Performance Lab Web Site

By Tracy Zafian, UMTC Research Fellow

Photo Source: Shannon Roberts, Human Performance Lab, UMass Amherst

The Human Performance Lab (HPL) based at the University of Massachusetts-Amherst has a brand new look! The HPL was originally created by Professor Donald Fisher in the 1990s and is world-renowned for its work on teen driver training. In 2016, the University of Massachusetts Transportation Center (UMTC) Affiliate Researcher Professor Shannon Roberts joined the HPL and now serves as the HPL co-director, overseeing research activities of the lab and day-to-day operations. Professor Roberts’ research is focused on driver feedback, in-vehicle interface design, automated vehicles, and teen/novice drivers. Her research group’s web site has information on her team and other interests.

With Dr. Robert’s arrival, the lab underwent significant changes. Upgrades include a new vehicle (2015 Ford Fusion), five new projectors with an expanded field of view of 330 degrees, new channels for displaying the side and rear-view mirrors and a new in-vehicle display.  The HPL has also obtained other new equipment including Virtual Reality (VR) headsets for delivering training and using with simulations, and a new heart-rate monitor to use with participants in lab studies.  Coming soon will be an instrumented vehicle for use with on-road studies.  The upgraded equipment will significantly expand the lab’s research capabilities.  One recent new area of research for the lab involves autonomous vehicles.  This is the transfer of driving control from driver to vehicle, and drivers’ awareness of their surroundings and ability to respond to potential roadway hazards as they switch from autonomous modes that require more attention and input from the driver, to those that require less attention.

As it has since its beginning, the lab, based in the Department of Mechanical and Industrial Engineering, continues to collaborate with other departments at UMass-Amherst including Civil Engineering, the UMTC, Computer Science, Electric and Computer Engineering, and Psychology.

Traffic Apps Impact on Neighborhoods and Safety

by Tracy Zafian, Research Fellow

Photo by Noe Veloso Fremont, CA Public Works Department

Smart phone apps, such as Waze and Google Maps, help drivers find the quickest routes to their destinations using real-time traffic data.  Sometimes this means that drivers are being directed off congested highways to streets through residential neighborhoods instead. Not everyone is happy about this, including traffic planners and people living in these neighborhoods who don’t want higher volumes of traffic on their streets.

News media have reported these impacts of traffic apps on Cape Cod neighborhoods, and in the Boston area.  Quoting Police Sergeant Charles Hartnett, head of Medford’s traffic division, in one news report: “For the residents, it’s a safety issue.”  Some communities are responding by restricting a cut-through and turning movements into residential neighborhoods during commuting hours when the traffic is heaviest.  In some places, certain streets are being changed to one-way roads as another means to divert traffic.  When such changes are made, transportation planners often share these updates with the app companies so that their maps and algorithms can be adjusted accordingly.

The traffic apps can also present a challenge to safety officials in emergency situations.  For example, in the Los Angeles area, while officials were busy fighting wildfires, they implored residents to ignore the apps that were directing them to lightly traveled roads in the fire zones, and put up message signs telling drivers “Don’t Trust Your Apps.” As described in this USA Today article, the fires and evacuation orders were the reason the traffic volumes is these areas were so low.  In Vermont, the shortest way isn’t always the safest way.  Cars have been abandoned because the driver followed Google maps, only to end up on a road that was not maintained in the winter.

Mutual Aid During the Winter – Lending a Hand

by: Matt Mann, Research Program Coordinator


A blaze recently destroyed the Sandisfield highway garage, leaving the town without access to trucks for snow removal.  Abutting towns and others have stepped in to offer services to assist Sandisfield with their snow removal needs.  Towns like Huntington, Northampton, Leominster, Beckett and others have posted on the One Center Baystate Roads listserve the various services offered for aid (e.g. equipment and staff) to help keep the roads clear and safe.  In Massachusetts, there are two types of Intrastate Mutual Aid Agreements that Towns can participate in: Statewide Mutual Aid Agreement and Public Works Mutual Aid Agreement.  Many Massachusetts towns have signed one of these documents to provide assistance to another town that is in need of equipment, staff, traffic mitigation, due to a natural disaster, fires etc…

MassDOT has also provided aid to Sandisfield.  Speaking with Kathy Stevens, District 1; “ MassDOT has committed two weeks of salt and plowing services to the town.”  This is not unusual for MassDOT to offer these services.  Historically they have offered other services as well, including traffic and safety mitigation.