Centerline rumble strips have been shown to reduce lane departure crashes by as much as 25% on rural roads, and are now being installed on undivided, rural, two-lane highways in Massachusetts as appropriate.
Improving safety, at a low-cost, can reduce crashes and save lives. In the U.S., 60% of crashes on rural roads result in a fatality. Of these fatal crashes, approximately 90% are on two-lane roads. Lane departure crashes from vehicles crossing over the centerline on undivided, two-lane, rural roads have been proven to decrease with the installation of centerline rumble strips (CLRS). This reduction can be as high as 25% along certain rural roads, and even higher when CLRS are installed along with shoulder rumble strips (SRS).
Many factors contribute to drivers crossing over the center yellow line, including speeding, fatigue, and drowsiness, and distracted driving. Some common techniques on the roads now that try to mitigate lane departures and improve safety include, but are not limited to centerline and edge line pavement lane markings, higher retroreflectivity of traffic signs (for day and nighttime visibility), and vertical reflective panels. All of these have had some success. A number of studies, however, have shown CLRS to be more effective along certain rural sections of highways, in decreasing lane departures.
The purpose of CLRS is to prevent vehicles from crashing head-on or sideswiping each other. Vehicles tend to veer outside of their lane on all types of roadways, especially on undivided, two-lane rural highways where cross-over crashes are most common. CLRS can also act as a traffic calming tool. Similar in design to the rumble strips on the shoulders of Interstates and other limited access highways, CLRS are located along the centerline. With either placement, the objective of the rumble strips is to alert inattentive drivers that they are veering outside of their lane, and ideally help them correct this action before a crash occurs.
The main reason for CLRS’ effectiveness is their design, specifically the vibrations and noise when tires cross over them. However, this noise has also been a major reason why CLRS are not used on more roads. Abutters and businesses have complained about CLRS being too loud as vehicles cross over them. California Department of Transportation (CalTrans) and Minnesota DOT (MnDOT) have conducted research on creating effective, quieter CLRS. MnDOT has developed the sinusoidal wave-shaped rumble strip. Some study results have shown a decrease in noise levels outside the vehicle, as vehicles cross over these sinusoidal rumble strips, while the CLRS still maintain the effectiveness by alerting drivers of lane departures. In addition to noise, another concern of CLRS is the potential reduction of visibility of the centerline yellow strip, though, in a survey by the Insurance Institute for Highway Safety, some respondents reported that the visibility of the centerline yellow strip in the rain was better over CLRS than on flat pavement.
MassDOT, along with other DOTs, continues to develop and implement CLRS on their rural, undivided, two-lane highways. MassDOT currently considers implementing CLRS on an as needed basis. Decisions about where to install CLRS are based on a couple of variables, including lane departure crash data and land use (regarding the noise factor). As discussed with Bonnie Polin, MassDOT Highway Division Manager of Highway Safety, CLRS were recently included in a paving project along sections of Route 140 in Gardner and Winchendon. CLRS are easier and more cost effective to install when a roadway is being re-paved as was the case along Route 140. As MassDOT updates its Strategic Highway Safety Plan, CLRS are referenced as a safety measure to prevent lane departures. MassDOT will continue to support and install CLRS on their secondary roads, where appropriate.
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.
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.
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.
In March 2018, an Uber Volvo operating in automated driving mode, with a driver at the wheel, hit and killed a pedestrian in Arizona. It was the first autonomous vehicle (AV)-related pedestrian fatality. There have been other crashes involving autonomous test vehicles and additional fatalities involving lower-level automated vehicles since. Also in March, a driver in California was killed when his Tesla, in autopilot mode, crashed into a concrete highway lane divider and caught fire. Last month, a Tesla, in autopilot mode, crashed into a parked firetruck in Utah and into a parked police car in California. Injuries were minor in these instances.
All of these crashes have occurred while there has been a driver at the wheel making decisions about when to use and disengage the automated driving assist system. As reported in a USA Today article, following the Utah firetruck crash, Tesla issued a statement saying, “When using Autopilot, drivers are continuously reminded of their responsibility to keep their hands on the wheel and maintain control of the vehicle at all time,” and, “Autopilot is designed for use on highways that have a center divider and clear lane markings.” These conditions are not always met when crashes occur; for example, the driver in the Utah crash admitted to being distracted by their phone before the crash. From the National Transportation Safety Board’s preliminary findings from investigating the Uber pedestrian crash, there was no warning given to the safety driver before the crash. Current AV technologies, such as Tesla’s Autopilot, are referred to by car manufacturers as “driver assistance systems” but it is not clear that all drivers understand their limitations, including the need for drivers to monitor the driving environment and stay involved in the driving process.
The Society of Automotive Engineers has developed a classification system for autonomous vehicles. The classification includes six levels (Level 0-5); with Level 5 being fully autonomous and Level 1, containing some automated features such as adaptive cruise control and parking assist. Most current automated driver assistance systems are Level 1 or 2, meaning that drivers still need to be actively involved.
Driver assistance systems and autonomous vehicles hold great promise for improving safety and mobility, but AV technologies are still relatively new, and numerous challenges remain. A number of universities and researchers in Massachusetts are exploring this topic. In April, a commentary by MIT AgeLab researchers, “People must retain control of autonomous vehicles,” was published in Nature magazine (link is for the article). In their remarks, Dr. Ashley Nune, Dr. Bryan Reimer, and Dr. Joseph Coughlin, Age Lab Director and UMass Transportation Center Research (UMTC) Affiliate, focused on two areas – safety and liability – that need urgent attention as policies and regulations are developed for autonomous and semi-autonomous vehicles. They write that, in their view, “some form of human intervention will always be required. Driverless cars should be treated much like aircraft, in which the involvement of people is required despite such systems being highly automated. Current testing of autonomous vehicles abides by this principle. Safety drivers are present, even though developers and regulators talk of full automation.” The researchers’ piece ends with key points for policymakers preparing AV legislation to consider:
Driverless does not, and should not, mean without a human operator
More information should be shared with operators/drivers about how well different autonomous and driver assist systems are working, including their reliability and limitations
Operators should need to demonstrate that they understand the autonomous and driver assist systems in their vehicles and should be tested on their understanding and competence at periodic intervals
Remote monitoring networks should be established and shift time guidelines considered for workers monitoring AVs.
In May, a forum held at Harvard University’s T.H. Chan School of Public Health on “Self-Driving Cars: Pros and Cons for the Public’s Health.” (A recording of this session and a transcript are available at this link.) Dr. Jay Winsten, Associate Dean for Health Communication at Harvard, said there is hope right now around the potential for autonomous and highly automated vehicles to reduce traffic deaths. He also addressed the hype around this: “I think both the media and some of the manufacturers and developers have been going a little too far in setting public expectations for what to expect, especially in the short-term and in the medium-term.” The panelists discussed that initially most vehicles will be highly automated (SAE Level 2), not autonomous (Level 3-5), and the deployment of the autonomous vehicles is likely to occur first for long-distance, highway-based commercial transport and in urban areas for shuttles and other short-distance trips. There are some challenges including the current reliability and drivers’ understanding of AV technologies, including the need for drivers to stay alert while behind the wheel and the safety of vulnerable road users. There are also concerns regarding regulation. The federal government through the National Highway Safety Administration has developed some guidelines regarding autonomous vehicles and automated driving systems. However, there are currently no federal regulations in place regarding autonomous vehicles. Therefore, currently regulations are primarily set at the state level.
As described in an earlier Innovative Outlook article, Governor Baker and Massachusetts state officials have largely taken the approach that it is better not to regulate AVs through legislation, as the technologies are still evolving and legislation can be difficult to modify once passed. Panelist Deborah Hersman of the National Safety Council, shared those concerns, saying “We’ve got to find out how to do this differently” so that any regulations keep up with changing technology. Herman also urged there be more transparency and data sharing regarding specific AV technologies and how well they perform, saying that NTSB investigations after a crash can be challenged by lack of access to such data.
In June 2018, MassDOT entered into a Memorandum of Understanding with several municipalities to help facilitate and expand autonomous vehicle testing on roadways in Massachusetts. As described in a MassDOT blog article, “Following the signing of this MOU, MassDOT and the participating communities will finalize a universal application for companies to use when seeking to test autonomous vehicles and the participating municipalities will identify locations and roadways suitable for autonomous vehicle testing. ‘This agreement will allow companies to responsibly develop and test autonomous vehicle technology in Massachusetts, while ensuring there are uniform safety guidelines in place,’ said Governor Baker [at the MOU signing] . ‘The MOU builds on the existing autonomous vehicle testing framework while simplifying the process for municipalities to work with innovative companies that are seeking to advance transportation, create jobs in our nation leading innovation economy, and improve our quality of life in the Commonwealth.’ …Said Lieutenant Governor Karyn Polito, ‘By creating a standardized process and working collectively with local officials, we can generate economic growth and support our communities as they play a role in the future of innovation and motor vehicle automation.’ Fourteen communities signed the MOU initially, including Boston, Worcester, Arlington, Boston, Braintree, Brookline, Cambridge, Chelse, Medford, Melrose, Newton, Revere, Somerville, Weymouth, Winthrop, and Worcester. In addition, the Massachusetts Department of Conservation and Recreation also joined the MOU, allowing Commonwealth-owned parkways to be available for autonomous vehicle testing.
Most people outlive their ability to drive by seven to ten years. This important statistic from the American Automobile Association (AAA) was cited by Michele Ellicks of the Massachusetts Registry of Motor Vehicles (RMV) at the April 2018 MassDOT Innovation and Mobility Exchange, at a session on Safe Driving for Seniors and People with Disabilities.
There were more than 40 million drivers age 65 years and older in the U.S. in 2015, according to the Federal Highway Administration (FHWA). This population is expected to increase significantly in coming decades. AAA has estimated that by 2030, there will be more than 70 million people in the U.S. in this age group with approximately 85-90% of them licensed to drive. In 2016, 18% of all traffic-related fatalities in the U.S. involved people age 65 and older. In Massachusetts, 16% (133) of all traffic fatalities in the state involved people age 65 and older. Over half (54%) of those fatalities were for those age 65 to 74; the other 46% were for those age 75 and older.
Nationally, the fatality rates per 100,000 people are higher for males than females and generally higher for people age 80 and over than for those 65-79 (see chart below). The death rates increase with age because older people have more physically frail and are more likely to die from injury, as found in this study from John Hopkins School of Medicine. Older drivers are also more likely to be involved in at-fault crashes as a result of physical or cognitive impairments. The fatality rates for females fall slightly from age 80-84 to age 85 and older because females limit or cease their driving in their upper 80s more often than males.
Intersections can be especially difficult for older drivers to navigate. Extensive research conducted at the University of Massachusetts Amherst on driving simulators and on-road has shown that older drivers do not look as often as other drivers towards their turning direction or other vehicles when turning at T-intersections or four-way intersections. As a result, older drivers may be more likely to be involved in traffic crashes.
UMass Amherst researchers working under the supervision of Dr. Michael Knodler are currently investigating older drivers’ crashes during left-turns at signalized intersections; using data gathered from their vehicles and the drivers themselves as part of the SHRP2 (Strategic Highway Research Program 2) project to collect naturalistic driving data on over 2,300 drivers at six cities around the country. The researchers hope this study will help with understanding why and how left turns across path crashes at intersections are more likely for older drivers.
In previous older driver research conducted at UMass Amherst, Dr. Matthew Romoser conducted one study on drivers age 72 to 87 and a comparison group of drivers age 25 to 55 for his dissertation, and then a follow-up study with the older drivers as a post-doctoral researcher. Romoser’s first study, conducted with his advisor, Dr. Donald Fisher, UMass Transportation Center (UMTC) Research Affiliate and UMass Amherst Human Performance Laboratory (HPL) Director, found that the older drivers took fewer roadway glances towards potential hazards than younger drivers while turning. Romoser also found that providing active training and customized feedback regarding their driving to the older participants led to significant improvements in their glances both in a driving simulator and on-road, towards potential hazards as they approached and went through intersections. Romoser’s follow-up study, conducted two years after the first study with the same older drivers, found that those drivers who received active training in the first study still made 50% more glances towards potential hazards than they did before training two years earlier.
The benefits of training programs to help older drivers stay safe at intersections was further examined in a study by past HPL researchers Dr. Siby Samuel and Dr. Yusuke Yamani, with Dr. Fisher. This research found that training programs, such as Dr. Romoser’s, which help improve older drivers’ glance behaviors at intersections, can be effective even though they don’t address underlying declines in cognitive, visual, and motor functions for these drivers as they age. The researchers found some evidence that these training programs are effective because, through the training, drivers learn to decouple their hand, foot, and head movements at intersections, and that doing so may help reduce the impacts of cognitive, motor, and visual declines on their driving.
This research is promising and suggests that some types of training may help older adults safely continue to drive longer than they would be able to otherwise. In Massachusetts, various measures have been taken to promote older driver safety. Under state law, for drivers age 75 and over driver license renewals must be done in person and they include an eye exam. The RMV holds free workshops around the state on issues facing older drivers, including if and when an older person should give up driving.
For adults who do stop driving for safety reasons, MassMobility is a state initiative to improve the transportation options for adults who don’t have a car. The options include both traditional transportation providers such as buses and paratransit and also newer alternatives such as Uber, Lyft, and other Transportation Network Companies (TNCs). A number of sessions at this year’s Innovative and Mobility Exchange discussed alternatives for meeting transportation needs for this population. Options included using TNCs to provide rides outside of regular bus service hours and TNCs partnering with senior centers and other agencies to offer rides to people who otherwise might not be able to access (because they don’t have a smartphone or credit card) services from companies such as Uber and Lyft.
by Tracy Zafian, Research Fellow, and Courtney Murtagh, UMTC Intern
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.
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.
The Insurance Institute for Highway Safety (IIHS) has updated its summary on large truck crashes and fatalities to include 2016 data from the Fatality Analysis Reporting System (FARS) maintained by the National Highway Transportation Safety Administration (NHTSA). The FARS data show though the number of deaths from large truck crashes has decreased nationally over the last 30 years, the last few years have seen an increase.
In 2016, a total of 3,986 people died in large truck crashes. Two-thirds of these deaths were occupants of cars and other passenger vehicles, 17 percent were truck occupants, and 16 percent were pedestrians, bicyclists, or motorcyclists.
According to IIHS’s analysis of the 2016 FARS data:
The number of people who died in large truck crashes was 27% higher in 2016 than in 2009, when it was the lowest it had been since the collection of fatal crash data began in 1975.
The number of truck occupant deaths was 47% higher than in 2009.
73% of deaths in large truck crashes involved tractor trailers.
62% of large truck occupant deaths occurred in single-vehicle crashes.
67% of large truck occupants that were killed in multiple-vehicle crashes were in a collision involving another large truck.
In its summary, the IIHS writes that “truck-braking capability can be a factor in truck crashes. Loaded tractor-trailers take 20-40% farther than cars to stop and the discrepancy is greater on wet roads or with poorly maintained brakes. Truck driver fatigue also is a known crash risk.”
The recent FARS data for Massachusetts shows that the number of fatal crashes in-state involving large trucks declined from 31 crashes in 2013 to 25 crashes in 2016. Over the same period, the number of truck occupant deaths from these crashes decreased from 4 to 2. This indicates that many of the people killed in the crashes involving large trucks were outside of the trucks, as occupants in other vehicles or as motorcyclists, bicyclists, or pedestrians.
In early April, the University of Massachusetts-Amherst School of Public Health and Health Sciences hosted a symposium on “Marijuana Legalized: Research, Practice, and Policy Considerations” to examine and discuss the potential public health and transportation safety impacts of marijuana legalization in Massachusetts. Massachusetts legalized marijuana for recreational use through a ballot initiative in the November 2016 election, and retail marijuana sales were permitted in the state in July 2017.
The keynote speaker at the symposium, Darrin Grondel, heads the state Traffic Safety Commission in Washington State and has over 25 years of traffic safety and law enforcement experience. His talk and webinar held the same afternoon, focused on the issues and impacts of impaired driving and drugged driving, and considerations for states developing policies and regulations in response to marijuana legalization. The slides from the webinar are available here. Washington State was one of the first states to legalize marijuana for recreational use, in 2012, and his presentation focused on Washington’s experiences after legalization. For example, 2014 FARS (Fatal Accident Reporting System) data for Washington revealed that speeding occurred in 35.8% of all fatal marijuana driving cases compared to 25.9% of non-alcohol or non-drug cases. Also, in Washington, after legalization, more drivers were found to be THC-positive one year after retail sales began, in 2014 than immediately before the sales. THC — tetrahydrocannabinol — is the principal psychoactive chemical compound in marijuana.
Unlike with alcohol and Blood Alcohol Concentrations (BAC), there is no THC-level that has been scientifically proven to be the level above which a driver would be significantly impaired. Alcohol stays in the bloodstream whereas THC goes to fat cells including in the brain. As discussed in a previous Innovative Outlook article, there are tests and technology, including smartphone apps for assessing impairment.
Other presenters at the symposium included Professors Jennifer Whitehill and Elizabeth Evans, from the UMass-Amherst School of Public Health and Health Sciences, and Cheryl Sbarra, senior staff attorney and Director of Policy and Law with the Massachusetts Association of Health Boards. Professors Whitehill and Evans are currently finishing a study with the UMass Donahue Institute and the Massachusetts Department of Public Health to estimate marijuana use rates before legalization. As reported in Daily Hampshire Gazette, Whitehill did not discuss any detailed results but she did speak about some general findings and areas for future research. From that news story: “One thing Whitehill noted is that when looking at fatal motor vehicle crashes, more attention needs to be placed on testing for marijuana and other drugs so as to understand the impact that they might be having on drivers.” She indicated that currently, only about 75% of drivers killed in a crash are tested for drug use after the crash. For non-fatal crashes, almost no drivers are tested for drugs. Drug testing more drivers in non-fatal crashes are one potential future research area. Another is the development of better quantitative methods and measurements for assessing impairment resulting from marijuana use.
For their presentations, Professor Evans discussed gender differences with regards to marijuana use, and lawyer Sbarra talked about municipalities regulating marijuana at the local level.
Among those attending the symposium were local health officials, local police, representatives from the marijuana industry, academic researchers and two members of the Massachusetts Cannabis Control Commission which is charged with implementing and administering laws for adult marijuana use and access in Massachusetts.
Winter in Massachusetts has just recently ended, but already communities are starting to plan and budget for their roadway snow and ice removal next year. Road salt and salt and water mixtures have long been used to help keep roadways clear and safe during the winter. However, there are now some grain and sugar based-options that when combined with salt can be more effective than salt or salt brine alone, and more sustainable as well.
One issue with using salt for road deicing is salt’s corrosive impact on metal, including vehicles and roadway infrastructure. Another concern is the polluting impact that road salt runoff as snow and ice melts can have on waterways, ecosystems, and wells. Through its Salt Remediation Program and commitment to environmental stewardship, MassDOT has established specific initiatives, as the program website says, that is aimed at “promoting the effective and efficient use of deicing chemicals.” One of the initiatives was the creation of the Snow and Ice Materials Usage Committee. This committee is charged with examining Best Management Practices for snow and ice removal, evaluating potential alternative roadway deicing options, and reviewing and revising current deicing policies.
Different Departments of Public Works (DPWs) have tried combining different agricultural materials, such as beet juice, beet molasses, cheese brine, and others, to their road salt to create better deicing mixtures. These agricultural additives contain carbohydrates that work chemically with road salt to lower the freezing point of water. These liquid mixtures can be sprayed on streets in advance of storms, which reduces salt bounce and helps prevent ice from forming. Such mixtures are also less corrosive.
Beet-based deicing mixtures have long been popular in the Midwest. Here’s a 2008 NPR story on the use of beet juice for deicing in Ohio. The DPW in Waukesha, Wisconsin has used a beet juice-salt brine mixture it prepares itself, as has Washington, D.C. Some Massachusetts communities are now using commercially-prepared beet molasses mixtures. As reported in a recent Boston Globe article, Wellesley officials started researching carbohydrate-based deicing additives after hearing great things about their use in other parts of the country. Wellesley Highway Division general foreman Kevin Collins and his team have been happy with the product, Magic-0 (Magic Minus Zero), that they started using in 2017. The product combines sugar cane molasses and magnesium chloride into a liquid mixture. It has been used by many highway departments and state agencies throughout New England, New York, New Jersey, and Pennsylvania. The town of Lexington, under DPW superintendent Marc Valenti uses something similar. Another popular deicing product made from beet molasses is Beet Heet. Beet Heet has been used by over 200 agencies in 8 states, mainly in the Midwest. The beet molasses products can offer the benefits of beet additives with better consistency and performance than beet juice mixtures. Some cities, such as Milwaukee, discontinued the use of beet juice additive after finding it clogged their truck sprayers.
Other tested deicing additives include cheese brine, which is the water remaining with cheeses such as mozzarella. Cheese brine has been used for deicing in Polk County, Wisconsin, since 2009, and was pilot tested a few years ago in Milwaukee. Pickle brine was pilot tested in New Jersey in 2014. Researchers at Washington State University have developed a deicer made of barley residue from vodka distilleries. With additives made from byproducts of food processing plants, location and access to the processing is a factor, and one reason, for example, that Wisconsin is the main adopter of cheese brine deicing. For local byproducts, the costs of the additives can sometimes be negligible as processing plants are happy to share their waste products in a win-win situation that can lower their own production costs as well.
As discussed in the Boston Globe, for now, the City of Boston currently primarily uses salt and sometimes a mixture of salt and water. However, the City’s Public Works Deputy Commissioner Michael Brohel says that carbohydrate-based additives could be in the city’s future. “We’re always open to testing out new methods,” says Brohel.
Baystate Roads plans to include discussion of deicing additives in its Snow and Ice Operations training for the next snow season.
The March Innovative Outlook (IO) discussed the first part of a University of Massachusetts (UMass)-Amherst study that evaluated different signage options to encourage more zipper merging when two lanes of traffic are merging into one. Here we discuss the second part of the study, involving testing the first phase results on a full-immersion driving simulator to analyze driver behaviors and decision-making in different scenarios where two lanes are merging into one.
The simulator evaluation was presented briefly at the Road Simulation and Safety Conference in the Netherlands in October 2017, and additional results were shown at the annual Transportation Research Board meeting in Washington, D.C. in January 2018.
Ideally, for zipper merges, similar levels of traffic occupy the left and right lanes approaching the merge. The vehicles from both lanes then take turns moving into the single lane, alternating from the left lane and then from the right lane, vehicle by vehicle, as in the two sides of a zipper coming together. For the first phase of the UMass study, drivers were surveyed about their perceptions and preferences of different road signs for a merge ahead and how they respond as drivers when shown different signs. One of the signs in the study was the W4-2 sign, also known as the “Lane Ends” sign, defined in the Manual on Uniform Traffic Control Devices (MUTCD); it’s the top sign in the figure. The other signs had been used in previous signage studies conducted by the Federal Highway Administration’s Human Factors Laboratory.
Based on the results of the earlier driver surveys, three different merge signs were used for the simulator part of the study: the standard W4-2 sign, a sign showing an alternative merge graphically, and a sign with “Alternate Merge” in words. There were 12 different scenarios tested on the simulator. In addition to varying the signage between the scenarios, two other variables were changed as well: which lane the driver’s vehicle started in at the beginning of the scenario (left lane or right lane) and the surrounding traffic conditions (vehicles in front of or adjacent to the driver’s vehicle). After the simulator drives, study participants were given a questionnaire regarding their perceptions of the different merge signs.
Not unexpectedly, since the standard merge sign (W4-2) is already in use, the standard merge sign had the strongest results in terms of driver recognition and comprehension. Drivers were found to be most likely to make lane changes upstream of the merge in the simulator scenarios with the standard merge sign. At the same time, however, the questionnaire results indicated that the standard merge sign was the least preferred sign to promote even merging from the left and right lanes. Another result, which differed from the results of the earlier driver surveys, was that the “Alternate Merge” sign with words was no longer among the most preferred signs for promoting even merging. Some participants in the simulator study felt that the “words were harder to process than pictures” and that the sign has confusing wording. The majority of participants preferred the graphic alternative merge sign for promoting even merging.
Two other interesting results were seen across the simulator scenarios: (1) participants were much more likely to switch lanes upstream of the merge intersection when they were following vehicles that had already merged than when they were adjacent to other vehicles, and (2) participants were more likely to switch lanes when their vehicle started in the right lane compared to the left lane. This second finding likely reflects the participants’ familiarity with merging into traffic from the right lane and is influenced too by the standard merge sign currently in use.
Overall, there were no significant changes in driver behavior upstream of the merge intersection. Still, a graphic alternative merge sign could have promise for encouraging more even, zipper merging, once drivers become more familiar with them. Additional study, potentially including field experiments, is needed to evaluate further the potential of alternative merge signs to improve traffic flow and safety and reduce traffic congestion at merge locations.
For additional information on this simulator study, you can contact graduate student Francis Tainter at firstname.lastname@example.org. The simulator study has been accepted for publication in the Transportation Research Record.
We’ve all had the experience of having to drive around a city looking for on-street parking near our destination. Having limited availability of parking can lead to increased traffic congestion and vehicle emissions and decreased safety while drivers are distracted and looking away from the road to find parking. The City of Boston, as well as the Commonwealth (including MassDOT), have all been looking for ways to reduce vehicle emissions and improve driver safety. Variable parking meter pricing by municipalities may help.
The City of Boston recently completed a year-long pilot study testing higher parking meter pricing in the Back Bay and Seaport neighborhoods. The final report of the study is available online here. A main goal of the study was to increase the availability of on-street parking with 1-2 on-street parking spaces per city block being open at all times, equivalent to a parking occupancy rate of 60-80%. The City also sought to increase road safety by reducing distracted driving caused by drivers looking for parking and to reduce traffic congestion by decreasing illegal parking and the time to find parking.
For the study, the City raised the metered parking prices in the Back Bay area and kept the higher price for the whole pilot year. With the increased pricing, the study achieved its stated goals. With the higher meter charges, there were more open on-street parking spaces for residents and business customers. There was also a reduction in illegal parking, in illegal parking in loading zones, in double parking, and an overall decrease in traffic congestion.
In the Seaport area, the City used a more dynamic pricing model, varying the meter prices from block to block and adjusting them every two months to try to maintain 60-80% on-street parking occupancy. During the study, the dynamic pricing generally did not lead to more parking availability. The on-street parking occupancy in many of the zones increased from January to October 2017, even though the meter prices were raised repeatedly. Parking occupancy fell during the final two months of 2017, though it’s not clear if that was due to the higher prices. Other factors could be an ongoing construction project that impacted parking availability, and seasonal demand fluctuations in the Seaport area. Overall, during the study, the number of parking meter transactions decreased. It is possible that many drivers going to the Seaport area were not aware of the differing and changing prices for different streets. As in the Back Bay, the amount of illegal parking fell significantly during the study.
During the study, public outreach sessions were held in the Back Bay and the Seaport neighborhoods. Both positive and negative feedback was received, with the negative feedback focused on the parking rate increases in these neighborhoods when other neighborhoods kept their old parking prices. Despite the latter feedback, the City considers the pilot program to be a success overall. When announcing the study results, Boston Transportation Department Commissioner Gina N. Findaca shared the City’s findings that the parking pilot program was “an effective tool to reduce congestion, improve safety, and open up more parking in our busiest neighborhoods” and “this program makes better use of our limited curb space and helps our business districts and neighborhoods thrive by making sure drivers can easily find a spot and that pedestrians and cyclists are not adversely impacted by double parking.”
Parking meter revenues rose by $5.7 million in the Back Bay and by $300,000 in the Seaport area during the pilot year. These funds will be used for a variety of projects to improve transportation mobility including for sidewalks, bus lanes, buses, and bridges.
There are other cities, including San Francisco, New York, and Los Angeles, that have introduced dynamic meter prices in popular neighborhoods and during times of peak demand to help address parking shortages and encourage other transportation modes.
Boston’s leadership is now considering possibly continuing the differential pricing in its current locations and perhaps extending it to additional parts of the city.