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Between 2018 and 2019, MnDOT installed a lane constrictor design at 66 side-street, stop-controlled intersections in Minnesota. The lane constrictor design narrows the lane width for mainline approaches via a striped median with centerline rumble strips. By narrowing the mainline lane, the goal of this design is to encourage mainline traffic to slow down as it approaches the intersection. The striped median also provides greater separation between mainline directions and draws more attention to the location of the intersection. Following the installation of lane constrictors at MnDOT intersections, overall crash rates have seen little change but there have been decreases in fatal and serious injury (KA) as well as fatal and all injury (KABC) crash rates. These results indicate the addition of lane constrictors have a positive impact on crashes by reducing the severity of crashes, swapping injury crashes for property damage only crashes.

Recent changes in laws regarding the use of volatile organic compounds impact the type of pavement marking material that many communities use to mark or delineate their roads. This report presents information on the various types of pavement marking materials available and summarizes information on pavement marking material terminology, the various types of pavement marking materials, their durability, and their retroreflectivity. The report explains changes in formulas relating to laws regulating the use of volatile organic compounds, as well as the impacts of those changes. Additionally, it includes a list of best management practices. This report indicates that for low-volume roads [annual average daily traffic (AADT) of 10,000 or less], a conventional product, such as paint, may be the most cost-effective material. For roadways with higher volumes (AADT of 10,000 or more), a more durable product, such as epoxy, tape or thermoplastics, may be more cost effective and may reduce worker exposure to traffic.

In pursuit of unimpeded high peak traffic flow, the "Design Guidelines for Super Two Highways" (Ekem, 1998) suggested several treatments for the right side of the roadway. But the left side is where drivers experience great speed differentials between their own vehicles and oncoming traffic. The authors examined centerline treatments and possible recommendations for Super Two guidelines. The current US standard (12-ft lane/4-in. dashes) was compared with combinations of wider lanes, wider dashes, and buffer areas. With each of the centerline treatments examined, participants kept the left side of the vehicle in the approximate center of the lane. All treatments resulted in shifting the center of the lane farther from the centerline than it was in the standard condition. Two conditions appear to be most effective in keeping drivers away from the centerline: 1) 14-ft lanes with both longitudinal rumble strips and 4-in.-wide dashes marking the centerline, and 2) 12-ft lanes with 4-ft buffer marked by 4-in.-wide dashes. However, implementing any of the centerline treatments should result in vehicles driving farther from the centerline, thus making it less likely that drivers will meet an oncoming vehicle. Data were gathered in a driving simulator. Further testing should be conducted in real driving situations.

This report presents a study of the impact lane markings and signing have on driving behavior at a two-lane roundabout located in Richfield, Minnesota. After its completion in 2008, this roundabout sustained a suspiciously high amount of crashes. In response, through this study, engineers experimented with changes in the roundabout's signs and lane markings, as roundabout design regulations are relatively lax and nonspecific in contrast to those for standard signalized intersections. An observational study was conducted that reduced 216 hours of before and after video records of the roundabout into a database of all the violations committed by drivers. Along with the observational data, crash records were analyzed and demonstrated that improper turns and failing to properly yield account for the majority of collisions. The changes implemented in the approaches to the roundabout and specifically the extension of the solid line seems to have reinforced the message to the drivers that they must select the correct lane before approaching the roundabout entrance. Although choosing the correct lane does not directly address yielding violations, it does reduce the occurrence of drivers conducting an improper turn and to some extent reduces the need for a driver to change lanes within the roundabout. The implemented changes produced a 48% reduction in normalized occurrences of improper turns, and a 53% reduction in normalized occurrences of drivers choosing the incorrect lane a month after the changes, while a year later, these reductions were 44% and 50%, respectively.

This Rumble Strip Noise Evaluation study presents results of sound level monitoring of three types of longitudinal rumble strips installed along the edge of two-lane rural roads in Polk County, Minnesota. The study is in response to objections raised by some landowners about the unwanted noise caused by vehicles traveling over rumble strips when they drift over the edge or centerline of the roadway. By changing and modifying the design, the ultimate goal is to provide the maximum safety by capturing the driver's attention through tactile and sound levels while minimizing the associated external noise generated by the rumble strips. Both exterior and vehicle interior sound levels were measured from three longitudinal edge of pavement rumble strip designs - California, Pennsylvania and Minnesota. Simultaneous digital audio files were also recorded. Three vehicles were used - a passenger car, pickup, and semi-trailer truck. Tests were performed at 30, 45 and 60 mph. Comparison of exterior and interior sound levels and audio shows that the Pennsylvania design is the quietest, both interior and exterior. The interior level of the Minnesota and California designs are similar but exterior levels are higher for the Minnesota design.

The objective of this project was to fully implement the Pavement Marking Management Tool by incorporating retroreflectivity and striping data (MnDOT and contractors) and simplifying the process of data collection, storage, and analysis. As part of achieving full implementation, the researchers provided training to MnDOT central office staff and staff in each of the districts. Improved pavement marking management has the potential to reduce MnDOT's costs, improve pavement marking performance, and in return provide a more efficient and safe driving experience for the traveling public. The result of this effort included a web-portal for submitting pavement marking data (paint and retroreflectivity), a geographic information system (GIS) web based tool to manage, view, and create reports on pavement marking data, and training on the data collection and tool. This technical memorandum presents project findings by task.

The goals of this project were to develop a large-scale vehicle-mounted robotic roadway message painter that could be run by a single operator, and to develop software to enable the device to automatically paint various messages and symbols on roadways. A completely new articulated robot arm was design and constructed, complete with a control system, operator interface, paint delivery system, truck mount, and mobile power supply. The system was thoroughly tested, and programs were written to allow the robot to paint several symbols and messages on a roadway. The programs were tested and fine-tuned indoors, and then tested outdoors once the robot was mounted on a truck. An important finding of this research is that the traditional markings used by MnDOT are not ideal for robot application. Robotic painting can be better accommodated by altering the outlines of the markings somewhat, and by using directional hash lines to fill in the symbols rather than solid paint. These machine-made markings are faster to apply and use less paint, and in the end may be more effective for motorists than the traditional markings. The robotic roadway painter developed during this project has the potential to completely change the way in which markings are painted on roadways. The device has demonstrated the ability to paint roadway markings using an articulated robot arm mounted on the front of a vehicle. Expected benefits of the deployment of such a device include improved operator safety, improved productivity, and improved flexibility in roadway marking operations.

This research effort provided the Minnesota Department of Transportation (MnDOT) with field data on the performance of pavement marking materials when used as rumble stripes on MnDOT roadways. These field efforts provide a perspective on the impact that both wear and winter maintenance practices have on retroreflectivity. Given that these markings were installed by a variety of MnDOT contractors and at different times and roadways, this report also serves to document the range of retroreflectivity provided to drivers at any given time on similar two-lane MnDOT roadways under the installation practice guidelines at the time of installation (2012 to 2013). More specifically, these measurements consider the difference in retroreflectivity provided by direction of travel (e.g., for the same marking, what is the retroreflectivity while driving northbound versus southbound?) and by roadway. The long-term evaluation collected field measurements both initially and after two winters (18 months) for centerline rumble stripes only and on seven segments over three different roadways. The in-service evaluation included new centerline and profile rumble stripEs, all of which were installed as part of the 2013 mill and overlay projects on bituminous surfaces within District 4 on two-lane MnDOT roadways. The retroreflectivity data were collected one winter (approximately 12 months) after installation with no initial measurement data being available. This effort included measuring the centerline rumble stripe performance over eight segments on four different roadways and the profile rumble stripe performance over 18 segments on 10 different roadways.

This Sinusoidal Rumble Strip Design Optimization Study presents results of sound level monitoring of four types of centerline rumble strips installed along Trunk Highway (TH) 18 in Mille Lacs and Aitken counties in Minnesota. This study is in response to objections raised by some landowners about the unwanted noise caused by vehicles traveling over rumble strips when they drift over the edge or centerline of the roadway. By changing and modifying the design, the ultimate goal is to provide the maximum safety by capturing the drivers attention through in-vehicle generated sound levels while minimizing the associated external noise generated by the rumble strips. Tests on TH 18 were performed with three different vehicles passenger car, pickup truck and a class 35 tandem dump truck. A single speed of 60 mph was used, as this was shown to provide the most meaningful data in the previous study. For each of the designs, an initial test was performed with vehicles traveling on normal pavement, followed by three passes on the rumble strip. Rumble strip designs 1 and 4 created lower exterior sound level increases but created interior levels similar to designs 2 and 3. The external results correspond to the depth of the rumble strip design, with designs 1 and 4 having a maximum depth of 1/8 inch less than designs 2 and 3. The interior sound level increases are similar for all four designs but vary by vehicle type. All of the designs created increases greater than 10 dBA for the passenger car, which is a desirable level for gaining attention of the driver. For the pickup truck, the interior sound level increases ranged from 4.5 to 6.8 dBA, while the increases for the dump truck ranged from 0.8 to 2.7 dBA.

Pavement marking is important for safety. Maximizing pavement marking performance in terms of increased retroreflectivity; within limited budget constraints; allows agencies to make better decisions toward providing more effective pavement marking performance on their roadway networks. This research project included conducting a survey of local agencies' pavement marking practices; mining existing National Transportation Product Evaluation Program (NTPEP) pavement marking data; and developing recommendations for future pavement marking research to support local agency needs. The NTPEP pavement marking performance data (related to pavement marking products used by local agencies in Minnesota) was analyzed to provide guidance to local agencies in terms of pavement marking material selection based on performance. The objective included determining pavement marking products of interest to local agencies and developing performance metrics for these products based on existing NTPEP data. The analysis performed on the NTPEP included modeling the deterioration behavior as a function of time. Also two-way ANOVAs were performed to compare various performance measures and the impact of different conditions on these measures.

The objective of this research was to conduct a field trial to evaluate the marking performance of different combinations of pavement marking materials and installation practices on challenging surfaces. The trial included a range of pavement marking products over varied roadway characteristics to assess the performance of different marking materials over different challenging surfaces by product, thickness, bead package, and whether or not a primer was applied. The research team worked with the technical advisory panel (TAP) to document pavement marking performance on several municipal roadways within the city of Eden Prairie and to organize and prepare for field testing of different marking materials on both a seal coat and micro surface roadway. These projects provide pavement marking performance on challenging surfaces information over different conditions (traffic levels and line types) apart from the MnDOT research test deck scenarios. These results provide MnDOT with a basis to consider pavement marking striping practices on challenging surfaces in terms of performance and cost. The high-build materials (primer plus VISILOK) and epoxies showed similar performance, which provides a good basis for material selection.

Pavement marking is an essential component of roadway construction and safety. The markings need to be visible (day and night) so that drivers can quickly identify where the markings are and determine what message is being defined. Good pavement marking provides critical elements to guide drivers on correct road paths, complement road signs that inform and warn drivers, and improve night driving conditions. This project's objective was to review existing pavement marking practices by local agencies in Minnesota (material selection, installation, specifications, and contracting procedures) to provide guidance for maintaining good pavement markings, thereby saving money and increasing road safety. The two specific objectives were as follows: 1. Review existing pavement marking practices in local agencies. 2. Develop recommendations for better management of pavement marking through the use of pavement marking management tools and coordination with the Minnesota Department of Transportation (Mn/DOT).

Minnesota Department of Transportation (MnDOT) staff has experienced that pavement markings do not perform well on seal coat and micro surface treated roadways, referred to as "challenging surfaces." This report serves as a beginning point and organized approach in addressing pavement marking practices on challenging surface roadways. The project objective was to document existing district practices and issues through several key tasks, which include a literature review, field review, and analysis of existing practice and performance. This effort identified the need for a field trial to provide control in the evaluation of these markings on challenging surfaces. An outline was developed for a future field trial effort, which will evaluate the marking performance of different combinations of pavement marking materials and installation practices. These project findings will be used in conjunction with the resulting field trial evaluations to improve MnDOT guidance and standard practice that will result in better performance, efficiencies, and roadway safety.

The thermoplastic pavement marking project, S.P. 2785-101 (T.H. 494), was let in 1963 as an experimental project under the Federal-aid highway program, with full Federal-aid participation in the cost of the work. This report covers application of the marking materials under this project and observations on performance during the first three months service.

A study performed by Davis and Fitzpatrick of Minnesota Mining and Manufacturing Company, in conjunction with the Minnesota Highway Department in 1952-1953, measured changes in reflectivity of highway sign materials due to "spray" and "splash" on a two-lane, rural highway with turf shoulders. The report, entitled "Sign Placement to Reduce Dirt Accumulation" is presented in HRB Bulletin 89, "Night Visibility", 1954. The purpose of this study was very similar - to investigate the pattern of spray from passing vehicles with respect to determining the optimum lateral and vertical placement of milepost markers for an Interstate-type highway with wider, paved shoulders.

This document summarizes the development of a scalable, reliable, and practical process for viewing, querying, understanding, and making consistent, objective, and cost effective decisions regarding pavement marking needs, durability, and quality. The research team developed a Web-based pavement marking management system through the development environment of Microsoft Visual Studio 2005 ASP.NET in conjunction with ESRI's ArcGIS Sever Enterprise 9.2 SP4 functionalities to manage and produce the GIS map resources. The web site hosting itself was done on a Windows based server operating Internet Information Services (IIS). The resulting web based mapping tool provides Mn/DOT staff the ability to map and query pavement marking retroreflectivity information and serves as a significant resource to both district and central office staff in developing short and long-term pavement marking plans.

Centerline rumble strips are being installed on rural Minnesota Highways in an effort to reduce crossover accidents. This study looks for possible detrimental effects on 2 and 3 wheeled cycles. Motorcycle accidents reports since centerline rumble strips first appeared on rural highways in 1999 revealed only 29 accidents on roads with the rumble strips. None of these reports implicated the rumble strips as a factor in the accident. There were also no visible indications of rider correction or overcorrection in 40 hours of roadside observations. Controlled conditions on a closed circuit supported this observation through 32 riders in all types of cycles and experience levels from 0 to 41 years of street riding. Interviews confirmed that the riders had no difficulty or concern with the rumble strips. The recommendation from this study is that cyclist should become familiar with the rumble strips in rider safety courses and driving examinations. There were no indications to impede the installation of rumble strips and no indication that signage is justified.

The installation and maintenance of pavement markings represents a significant financial investment for local agencies. Local agencies need a mechanism to better understand the value; cost; and need for markings along their roadways to make the best use of available budgets. This project developed a prioritization approach and spreadsheet tool (link provided in box 15) to assist local agencies in meeting this need. Multicriterion decision analysis using the simple additive weighting method was employed to assess the multiple factors/criteria that affect pavement marking decisions. An Excel spreadsheet tool was developed to implement this approach using different pavement marking alternatives; including centerlines; edgelines; centerlines and edgelines; high-visibility markings; and enhanced-durability markings. The criteria considered by the process include project type; County Roadway Safety Plan (CRSP) rating; functional classification; pavement condition; traffic volume; age of current markings; pavement width; preferences for marking costs; desired marking durability; and crash reduction potential. This tool is posted on the Local Road and Research Board (LRRB) website in the "Resources" section at the following URL: https://lrrb.org/resources/. Factor weights are used to assign a relative importance to each of these criteria for a respective alternative compared to other alternatives. The result is a performance rating score for each marking alternative relative to all model criteria and factors that provide users with information on the relative performance of different marking alternatives in comparison to one another and an estimated project cost for the highest ranking alternative for a site. The highest scoring alternative represents the marking that should be considered for use. Additionally; the tool ranks all sites being evaluated compared to one another based on the highest rating scores from each individual site.

The purpose of this report is to document the field evaluation of a thermoplastic pavement marking material on a 2 year old asphalt pavement located on Cell 26 of MnROAD’s Low Volume Road. HMA pavement reconstruction occurred on the test cell in 2004, using 4 in. of Superpave HMA over a 12-in. Class 6-Special aggregate base. The structural design is based on 20-year ESAL’s of 110,000, according to the MnPAVE design software. The mixture design is identified by Mn/DOT designation SPWEB240B-R. On May 16, 2006 a total 524 square feet of inlaid thermoplastic pavement marking material was installed on Cell 26. This area included two crosswalks placed across both traffic lanes and a 2 x 100-ft segment installed in the left wheel path of the 80K load lane. The project was part of a partnership agreement between Mn/DOT and Decorative Pavement Marking, LLC of Plymouth, Mn. The purpose of the project was to evaluate the physical properties of the product, including friction resistance and the evaluation of the overall durability of the pavement surface. Integrated Paving Concepts Inc. of Vancouver, B.C., supported the project and assisted DPM in the installation process. During the period between May 16, 2006 and August 1, 2007 Cell 26 received 6,809 and 2,003 repetitions of the 80K and 102K truck configurations respectively.

The purpose of this report is to document the installation process of a thermoplastic pavement marking material on a 2 year old asphalt pavement and to provide an overview of historical information relating to the condition of Cell 26 up to the time of installation.

Appropriate deceleration on approaches to roundabouts is primarily accomplished through the use of applicable geometric design principles. However, traffic control devices (specifically signing and makings on approach) also serve a vital role in communicating to the approaching driver what speed profile should be anticipated. This report provides a resource for engineers to identify and select appropriate speed-reduction treatments for high- speed approaches to roundabouts. The research examines best practices and techniques that are the most effective at lowering approach speed.

This Technical Summary pertains to report 2020-09, Pavement Markings—Wet Retroreflectivity Standards.

Centerline rumble strips—grooves that are milled into roadways between lanes—alert drivers when their vehicles wander. They have proven effective in reducing accidents caused by vehicles crossing over into opposing traffic. Mn/DOT has installed these strips on several hundred miles of roadways, slowly phasing the practice in over a period of years.

Pavement markings are an essential component of highway construction and roadway safety. Drivers need to quickly identify where the markings are and what they are telling them. Good pavement markings provide critical elements to guide drivers on correct road paths, supplement road signs to inform and warn drivers, and improve night driving conditions.

This Technical Summary pertains to LRRB-produced Report 2018-21, “Investigating the Necessity and Prioritizing Pavement Markings on Low-Volume Roads,” published June 2018.