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

Uber, Lyft…Impacting Traffic and Economic Development

by Matt Mann, Research Program Coordinator



People are taking Uber, Lyft or Transportation Network Companies (TNCs) more these days and often to avoid both parking and drinking and driving.  Although the majority of users are urban base, demand has been increasing in suburbia for Ubering.  TNCs have changed the way people get around and have impacted traffic in many cities.  If these types of rides are a pre-cursor to autonomous vehicles, the additional passenger trips will continue to increase and will also impact economic development.

A recent U.C. Davis study that included 4,000 users in seven major metro areas—Boston, Chicago, Los Angeles, New York, the San Francisco Bay Area, Seattle, and Washington, D.C., between 2014 and 2016 – points to cities increasing in passenger trips and in population, but transit rides and taxi trips decreasing.  The TNCs are the main source that are accommodating the increase in trips and in-turn causing more urban traffic congestion.

This study also found that around 50% of these trips would not have happened at all or would have been done some other way, via transit, walking etc…This coupled with the dead head time, when no passengers are in the vehicle, the TNCs are having a dramatic impact on vehicle miles traveled and congestion.

Currently New York City is the only major metropolitan city that mandates TNCs to report their travel data.  Other cities are able to obtain data but TNCs are not required to share it.  Being able to access and analyze this data can be the key to determining current and future traffic impacts.

Massachusetts passed legislation in 2016, creating a regulatory framework for TNCs. Speaking with Katie Gronendyke, Press Secretary, Executive Office of Energy and Environmental Affairs, the MA Department of Public Utilities Transportation Network Companies Division  does require some TNC travel data to be reported:

274.12: Reporting Requirements

(2) Annually, a TNC shall report to the Division the following: (a) By February 1st of each calendar year, a TNC shall submit a report for the number of Rides from the previous calendar year, including: 1. City or town where each Ride originated; 2. City or town where each Ride ended; 3. Aggregated and anonymized trip route and length (miles and minutes); and 4. Location of Vehicle accidents;

(b) By March 31st of each calendar year, a TNC shall report its intrastate operating revenues for the previous calendar year. If a TNC fails to report its intrastate operating revenues to the Division by March 31st of any calendar year, the Division may estimate a TNC’s intrastate operating revenues. A TNC’s intrastate operating revenue shall include but not be limited to any Rider picked up at the following: 1. Airport; 2. Train station; 3. Bus terminal; or 4. Any other kind of port.

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.

Portland Maine – Thinking Ahead for Autonomous Shuttles

by Melissa Paciulli, Manager of Research




The Town Planner and Legislators are working together to be prepared for a potential autonomous shuttle that connects the Portland Transportation Center with the waterfront and downtown area to assist tourists. New legislation was drafted by Representative Heather Sanborn, which would allow cities and towns to start pilot programs in partnerships with state agencies with autonomous vehicles, as reported in the Portland Press.

The proposed legislation could set up Maine to be a leader in pilot programing for autonomous transit.  Companies such as the global data company Inrix, have been in touch with Town officials about collecting data on the city streets, necessary for autonomous navigation. There are no current companies lobbying for the first pilot in the area, however the legislation, which is slated for a January 2018 review, is a first step in the process of making this a reality.

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.

Distracted Walking: A Global Epidemic

By Courtney Murtagh, Tracy Zafian, and Matt Mann, UMTC Research Staff

Most of us are aware of the dangers of distracted driving, but distracted walking? Around the world and close to home, it’s a growing epidemic. More and more people are texting and using their phones while walking in intersections, creating unsafe situations.

source: Premier Insurance Corporation

A 2017 report by the Governors Highway Safety Association found that pedestrian roadway deaths in the US are now at their highest level in over 20 years, with more than 6,000 pedestrian fatalities in 2016. An article in the May 2017 MassDOT Innovative Outlook, discussed a number of contributing factors for this, including: more driving; alcohol use by drivers and pedestrians; lack of pedestrian visibility; and driver and pedestrian distractions.

Dr. Cole Fitzpatrick, a UMTC Affiliate Researcher, recently conducted a field study on the prevalence of distracted walking and its effect on driver behavior. The study included observations of a total of 1,386 pedestrian crossings and 890 pedestrian-vehicle interactions at seven different crosswalks on the UMass Amherst campus. The researchers found that nearly half of all pedestrians were distracted while crossing the street, with 22% of them talking to another person beside them, 16% using headphones, and 10% either texting or talking on their phones.

Cities have begun to take notice of distracted walkers and are looking for ways to improve intersection and crosswalk safety. In October 2017, Honolulu enacted a law allowing pedestrians who text on their phones while crossing the street to be fined $15 to $99 for doing so.  This new law is thought to be the first such law of its kind in the country. Prior to October,  Honolulu had more pedestrians being hit  by vehicles in crosswalks, than any other major US City. Local high school students were instrumental in pushing for this law. Kel Hirohata, a local high school teacher interviewed on National Public Radio recently, described how the Youth for Safety club at Waipahu High School spent more than a week watching fellow students as they left school. They noticed an alarming trend: many of their classmates staring at their phones while crossing the street. The Safety club members took note of the potential danger, and then followed up with a local councilmember who wrote a bill which then became the new law.

Legislators in other places have also proposed laws to curb texting while walking. In San Mateo County, California, County board members unanimously voted in favor of a resolution in September 2017 asking state lawmakers to pass a law banning cell phone use in crosswalks. Stamford, Connecticut is now considering an ordinance that would ban cell phone talking or texting while crossing the street and impose a $30 fine for offenders. In September 2017, New York State passed a law requiring the New York City Transportation Department to study and report on its efforts to educate drivers and walkers about the dangers of pedestrians distracted by cell phones.  In Massachusetts a bill was introduced this November to ban texting while jaywalking. No action has yet been taken on this proposed legislation.

It’s not just in the United States that officials are looking into distracted walking. Bodegraven, Amsterdam for example installed lights in the ground near crosswalks that would change colors with the traffic lights, so people looking down on their phones would be more aware of the nearby traffic and when it’s safe to cross.

LED sidewalk lights in Amsterdam. Source:


Live from NYC-Times Square – UMass Raises Awareness about Texting and Driving

Source: University of Masaschusetts-Amherst

By Melissa Paciulli, Manager of Research, and Tracy Zafian, Research Fellow 

UMass at Time Square! A billboard designed by UMass-Amherst students to raise awareness of the dangers of texting while driving is currently being displayed in Times Square in New York. The billboard will also be displayed on Route 9, Interstate 495 near Lawrence and Methuen and I-290 in Worcester, Massachusetts. Other locations around the country will also display the sign.

The billboard was created with the help of the UMass Adlab at the Isenberg School of Management at UMass-Amherst, under the guidance of Isenberg professor Elizabeth Miller by UMass student Kyle Pandiscio (’19) and now graduate Julia Keefe.  At the UMass Adlab, students develop advertisement and campaign images to market “change” for real-life clients.

As described in this UMass press release,  Keefe and Pandiscio won the Project Yellow Light billboard Public Service Annoucement (PSA) competition with a billboard design autocorrecting “Don’t Text and Drive” to “Don’t Text and Die” to enforce the concept that a texting accident can occur in a split second. Their billboard design was selected from 1,150 entries.  Pandiscio and Keefe realized the irony of creating a billboard when the campaign’s whole point is for drivers to keep their eyes on the road, so they maximized the impact by making the format the text message itself. “When people are driving, the last thing [we] want to do is create a billboard that is distracting,” Pandiscio told the Boston Globe.

The Project Yellow Light competition was sponsored by the Ad Council, the U.S. Department of Transportation’s National Highway Safety Administration, the National Organizations for Youth Safety, U-Haul, Mazda, Clear Channel, and I Heart Radio.  The contest included categories for video, radio and billboard PSAs, with entries submitted by high school and college students.

UMTC Affiliates & MassDOT Assistant Secretary Katherine Fichter Present at WPI Conference on Vehicle Automation

By Tracy Zafian, UMTC Research Fellow

In May 2017, Worcester Polytechnic Institute (WPI) held its second annual Connected and Autonomous Vehicles Summer School speaker series, sponsored by the Institute of Electrical and Electronics Engineers Vehicular Technology Society (IEEE VTS). The event included two days of lectures and discussions.

CAV intersection
Photo source: U.S. Department of Transportation
  • Danjue Chen, Professor at UMass-Lowell and UMTC Affiliate, discussed the impacts of connected and automated vehicles (CAVs) on traffic operations and highway traffic flow, and how CAVs can help optimize roadway capacity and traffic control. Professor Chen is the featured researcher in this month’s Innovative Outlook (IO).
  • Hossein Pishro-Nik, Professor at UMass-Amherst and UMTC Affiliate, spoke about Vehicular Ad Hoc Networks (VANETs) for vehicle-to-vehicle and vehicle-roadway infrastructure communications. His talk discussed the relationship between communications and safety in VANETs, how VANETs can be customized for different traffic conditions and individual drivers, and the issues of privacy in VANETs and Internet-connected devices and applications. Professor Pishro-Nik’s research is described in more detail in another post.
  • Jason Rife, Professor at Tufts University, presented information on different GPS-based technologies and applications that can assist with automated vehicles and navigation, even in dense urban areas with limited sky visibility.
  • Bob Sletten, Engineering Manager at Autoliv, a company that develops automotive safety systems for auto manufacturers, spoke about radar technology in automotive applications.
  • Akshay Rajhans, Senior Research Scientist at MathWorks, spoke about model-based design for connected autonomous vehicles. As described in the WPI conference program, “model-based design makes use of computational models of systems under design that are developed, optimized and checked after correctness specifications throughout the design cycle.”
  • Alexander Wyglinski, WPI Professor and organizer of the conference, provided an overview of vehicular communication systems and the fundamental concepts for understanding, designing, and implementing them.

The keynote speaker at the gathering was Katherine Fichter, Assistant Secretary for Policy Coordination at MassDOT. Ms. Fichter discussed the potential future impacts of driverless vehicles under different scenarios, including a Driverless Utopia and a Driverless Nightmare that were described in Driving Towards Driverless Cars, a blog by Lauren Isaac. Under these scenarios, autonomous vehicles are expected to improve roadway safety, increase vehicle miles traveled, and reduce greenhouse gas emissions, but there are other potential impacts that are less certain. For example, will more driverless cars reduce urban sprawl or increase it, and how will the mobility of low-income people be impacted? As Ms. Fichter discussed, there are questions as well about how autonomous vehicles will be regulated and insured. One big challenge is that current regulations are all based on the idea that vehicles have human operators; this will need to change.

GM Rolling Out AV Fleet

By Tracy Zafian, UMTC Research Fellow

General Motors Company (GM) announced in mid-June that it completed production of 130 self-driving Chevrolet Bolt electric vehicles for testing automated vehicle (AV) technologies on-road. These highly automated vehicles (HAVs) join GM’s more than 50 Chevrolet Bolts with AV technologies already operating on public roads in San Francisco, Detroit, and Scottsdale, Arizona. In April 2017, Spectrum, the flagship magazine for the Institute of Electrical and Electronics Engineers (IEEE), reported on GM plans to have as many as 300 more self-driving vehicles on-road, presumably including the recently completed 130 vehicles. According to Spectrum, GM would then have the largest HAV fleet on-road not only in the United States, but worldwide. Google-based Waymo has the second-largest AV fleet in the United States, with an estimated 160 vehicles on-road.

GM CEO & Chairman Mary Barra with a new Chevrolet Bolt AV (Photo by Paul Sancya, Associated Press)

In GM’s announcement regarding the 130 new self-driving Bolts, GM Chairman and CEO Mary Barra is quoted: “This production milestone brings us one step closer to making our vision of personal mobility a reality …. Expansion of our real-world test fleet will help ensure that our self-driving vehicles meet the same strict standards for safety and quality that we build into all of our vehicles.” CEO Barra has also said that “no other company today has the unique and necessary combination of technology, engineering and manufacturing ability to build autonomous vehicles at scale.”

The new self-driving version of the Chevrolet Bolt is the second generation of GM’s AVs and is capable of handling almost any roadway situation without human driver intervention. The new Bolts are equipped with the latest technologies in cameras, radar (LiDAR), sensors, and related hardware. “There are even a couple of cameras that are dedicated just to seeing traffic lights to make sure you don’t run red lights,” said Kyle Vogt, CEO of Cruise Automation, a self-driving software company that GM acquired in 2016. The GM HAVs always have an employee in the driver’s seat for safety reasons, just in case any intervention is needed. Almost all states with HAV regulations also have the requirement that a human operator be present.

In 2016, GM also partnered with and invested $500 million in ride-sharing company Lyft. In a recent Forbes article, Cruise CEO Vogt wouldn’t confirm a Reuters report that “thousands” of self-driving Chevrolet Bolt hatchbacks will go into service for ride-hailing company Lyft in 2018, but said it wouldn’t be surprising. “We’ve had a plan in place for a while and it’s going according to schedule. From what I can tell it’s much faster and going to happen much sooner than most people in the industry think,” Vogt said. “We’re planning to deploy in a rideshare environment, and very quickly.

‘Look Mom, no hands….’ TRANSFER CONTROL TO YOUR CAR? Not that far off in the future

lookmanohandsIn the fall of 2016, the US Department of Transportation announced new policies and initiatives for autonomous vehicles (AV) and AV research. The new Federal Automated Vehicles Policy is based on the US DOT’s view that  automated, autonomous vehicles can help promote safety, mobility, sustainability. With the increase use of AVs and semi-autonomous vehicles, there are some potential safety concerns as well, including relating to the ability of people using such vehicles to respond to potential hazards and potentially hazardous situations.

Siby Samuel, PhD, a UMTC Research Affiliate in Industrial Engineering at the University of Massachusetts-Amherst, and colleagues, including Shlomo Zilberstein in the Computer Science Department, have been studying the topic of semi-autonomous vehicles and safety for a number of years. Their research has focused on situations where the control of driving transfers to the vehicle in uncomplicated driving environments (such as a limited access highway), but where drivers still need to be prepared to take back control of the vehicle  to address potential hazards that arise.  This level of driving automation is known as Level 3 automation. Zilberstein and two of his graduate assistants, Kyle Wray and Luis Pineda, are researching how to transfer control “quickly, safely and smoothly back and forth” between the system and the person operating it. All of these studies were conducted on UMass’s Advanced Driving Simulator ( ).

“The real trend in artificial intelligence is to build systems that can collaborate with people,” Zilberstein said. (Daily Hampshire Gazette)

At the Transportation Research Board (TRB) Annual Meeting in January 2017 Dr. Samuel’s team presented two recent studies on Level 3 driving automation and the time it takes for drivers to be able to respond to potential hazards when the driving control of the vehicle needs to switch from the automated system to the driver.

An earlier study by Samuel and Zilberstein also looked at this transfer of control on the driving simulator.  Participants were instructed to transfer control to automation upon hearing an audio alert “transfer control”, and then later they were told with another audio alert “take over control” when they were to resume manual control of the vehicle. During the automated driving phase, participants were instructed to do tasks on a computer tablet. This study found that the minimum transfer of control altering time required for drivers in a Level 3 driving environment to respond to a potential hazard was 8 seconds when the hazard was expected, when the roadway environment was not changing during the transfer of control process, and when they were doing tasks on a computer tablet during the automation part of the drive. In other words, it took 8 seconds for these drivers to anticipate hazards at a rate equivalent to that of drivers who were manually driving their vehicles and weren’t distracted with in-vehicle tasks.   In one study presented at this year’s TRB meeting, Samuel and colleagues found that more informative audio alerts, for example a message telling a participant about at at-grade rail crossing or a lane reduction ahead could reduce the needed time for participants to respond to a potential hazard by as much as 40% or 4 seconds.

UMass Affiliate Researchers make headlines on driverless cars: (Daily Hampshire Gazette)

Written by Tracy Zafian, UMTC Research Fellow