Maintenance Operations, Materials and Construction

The 411 on Sign Management

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A revised handbook offers Minnesota cities and counties the latest tips on how to meet new sign retroreflectivity requirements, as well as the 411 on sign maintenance and management – everything from knowing when it’s time to remove a sign to creating a budget for sign replacement.

The best practices guide – produced in conjunction with a new sign retroreflectivity study – also offers case studies from around the state.

“The life cycle of traffic signs, from installation to replacement, is a pretty complex issue and it can be a challenge to get your arms around,” said Tim Plath, Transportation Operations Engineer for the city of Eagan. “This handbook really boils it down into some basic concepts and also gives you the resources to dig deeper if necessary. It’s a good resource to have at your fingertips.”

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This handbook updates a previous version issued in 2010, to include new FHWA  retroreflectivity and maintenance and management requirements and deadlines.

“Maintenance/management of a large number of signs can potentially be an administrative and financial challenge for many local road authorities,” explained Sulmaan Khan, MnDOT Assistant Project Development Engineer.

Here’s a video demonstration of a sign life reflectometer (the Gamma 922), another resource MnDOT has available for local government agencies. Cities, townships or counties may borrow the reflectomer by contacting the Office of Materials and Road Research, (651) 366-5508.

Related Resources

Traffic Sign Maintenance/Management Handbook (PDF)

Traffic Sign Life Expectancy – Technical Summary (PDF) and Final Report (PDF)

Gamma 922 demonstration (video)

Traffic and Safety

Six Ways to do Multimodal in Greater Minnesota

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Can rural Minnesota do multimodal?

You betcha, says a new study by University of Minnesota researcher Carol Becker, who compiled 65 examples of innovative multimodal rural and small urban transportation projects from around the United States.

The study, funded by the Minnesota Department of Transportation, looks at alternatives for promoting and strengthening multimodal transportation in rural and small urban areas. Becker developed these six case studies to showcase different modes and strategies:

Retrofitting Sidewalks

The city of Olympia, Washington, was mostly built during the automobile era. As a result, most of the city developed without sidewalks. In 2004, Olympia passed a voter referendum that linked enhanced parks with adding sidewalks throughout the city. The referendum was supported by parents who wanted safe routes to school for their children and by environmentalists who wanted alternatives to driving. But the key to voter approval was linking recreation at parks with recreation walking to and from the parks. The Parks and Pathways program is now retrofitting miles of sidewalks into neighborhoods.

A sidewalk that was built using utility tax funds on San Francisco Avenue in Olympia, Washington.
A sidewalk that was built using utility tax funds on San Francisco Avenue in Olympia, Washington.
Intercity Bus Service

North Dakota has the third-lowest population density in the United States. Despite this, it has a network of buses that connect small towns to larger regional centers. Such alternatives to driving allow residents — particularly elderly and disabled persons — to stay in their communities rather than move to large cities to access needed services.
InterCity

Senior Transportation

A nonprofit in Mesa, Arizona, implemented a program to reimburse eligible seniors for car trips provided by other individuals. The program was moved to the regional transit provider for expansion. It did not scale up well, however, and was recently replaced with the East Valley RideChoice Program, which provides seniors and disabled adults with  discounted cards for taxi service. RideChoice participants can receive up to $100 of taxi service per month for either $25 or $30, depending on their city of residence.

Photo courtesy of Valley Metro RideChoice
Photo courtesy of RideChoice
Integrating Highways into Small Town Fabric

One challenge to making smaller communities more walkable and pedestrian-friendly is that most small towns are built around MainStreethighways. In fact, unless a bypass has been built, the main street of a small town is also typically a highway. This creates a conflict between groups who want to move vehicles efficiently and groups who want pedestrian-friendly downtowns.

Oregon took two steps to help mediate this:

  • Added a functional classification to the Oregon Highway Manual for the portion of roadway that runs through small towns. This functional classification has very different design standards that can accommodate walking, biking, commercial activity along the roadway, parking along the roadway and many other small-town needs.
  • “Main Street: When A Highway Runs Through It” was written to help local governments understand their options for creating a multimodal environment and better advocate for their interests with the Oregon Department of Transportation. The document explains ODOT funding processes and  shows examples of design options. Local governments can then adopt these elements and standards into their local plans, which ODOT must work with when doing highway improvements.
Complete Streets

Clinton, Iowa, is a city with a population of 27,000 on the Mississippi River in eastern Iowa. In 1995, the rail yard closed, which provided an opportunity to redevelop land. The city created a comprehensive long-range plan that included remediating soil contamination, purchasing land for redevelopment, realigning two streets and increasing transportation choices with a “complete streets” design. The reclaimed land will support a multi-use path, sidewalks and connections to cross streets.

Approximately $50 million has been secured for the project.  A $2.7 million Transportation Investment Generating Economic Recovery (TIGER) grant was also received from the U.S. Department of Transportation in 2012 to pay for a multi-use trail with a direct connection to the Mississippi River Trail, decorative lighting and plantings. In the future, land will be sold for higher density, walkable development.

A look at part of Clinton, Iowa’s redeveloped old railroad area, now called Liberty Square.
Impact Fees for Funding Infrastructure

As resistance increases to broad-based taxes, there has been a shift toward funding transportation with fees linked to specific projects. Examples include:

  • Concurrency laws, which require capacity in governmental systems (either planned or existing) before development can occur. If capacity does not exist, development cannot occur. In the state of Washington, a number of cities use concurrency to set transportation fees paid by new development. Bellingham, Washington, uses this kind of system to raise funds for transportation projects.
  • Development impact fees. Contra Costa County, California, has a capital plan for transportation improvements and sets a fee that is paid by new development to fund that infrastructure. Fees vary from under $1,000 to over $15,000 depending on where new development is occurring. The county expects to raise more than $845 million in transportation dollars from 2014 to 2030 using such a mechanism.
  • Allowing local units of government to create special districts to fund transportation projects.
Related Resources

Rural and Small Urban Multi-Modal Alternatives for Minnesota – Final Report

Research, Traffic and Safety

Teen Driver Support System helps reduce risky driving behavior

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Although teen drivers make up a small percentage of the U.S. driving population, they are at an especially high risk of being involved in a crash. In fact, drivers between ages 16 and 19 have higher average annual crash rates than any other age group.

To help teen drivers stay safe on the road, researchers at the U of M’s HumanFIRST Laboratory have been working for nearly 10 years on the development of the Teen Driver Support System (TDSS). The smartphone-based application provides real-time, in-vehicle feedback to teens about their risky behaviors—and reports those behaviors to parents via text message if teens don’t heed the system’s warnings.

TDSS provides alerts about speed limits, upcoming curves, stop sign violations, excessive maneuvers, and seat belt use. It also prevents teens from using their phones to text or call (except 911) while driving.

The research team recently completed a 12-month field operational test of the system with funding from MnDOT. The test involved 300 newly licensed teens from 18 communities in Minnesota.

To measure the effectiveness of the TDSS on driving behavior, the teens were divided into three groups: a control group in which driving behavior was monitored but no feedback was given, a group in which the TDSS provided only in-vehicle feedback to teens, and a group with both in-vehicle and parent feedback from the TDSS.

Preliminary results show that teens in the TDSS groups engaged in less risky behavior, especially the group that included parent feedback. These teens were less likely to speed or to engage in aggressive driving.

Although these results demonstrate that the TDSS can be effective in reducing risky driving behavior in teens, Janet Creaser, HumanFIRST research fellow and a lead researcher on the project, stresses that technology is not a substitute for parent interaction.

“The whole goal of our system is to get parents talking to their teens about safe driving.” Creaser says. “And maybe, if you’re a parent getting 10 text messages a week, you’ll take your teen out and help them learn how to drive a little more safely.”

Read the full article in the November issue of Catalyst.

Traffic and Safety

How those little blue lights make intersections safer

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A story from WCCO-TV last week answered a question that has likely been puzzling many commuters passing through Ramsey County: what are those blue lights popping up on traffic signals?

The report explains that the blue lights illuminate when a traffic signal changes to red, allowing a patrol officer to witness and enforce a signal violation more easily and safely. What the report doesn’t explain is the safety benefits to be gained from increased red light enforcement.

In Ramsey County, the proposal for a recent large deployment of blue lights came from traffic engineers, not police.

“Our county safety highway program conducted by MnDOT indicated a lot of right-angle crashes related to people running red lights,” said Ramsey County Planner Joseph Lux. “These are typically the accidents with the severest injuries.”

As part of the statewide Towards Zero Deaths (TZD) initiative in July 2013, MnDOT worked with counties to develop safety plans that emphasize low-cost, high-value safety improvements.

A federal grant is helping fund the installation of 128 blue lights at 49 intersections in Ramsey County (see locations) over the next two weeks. Deputies will begin enforcement later this month, but the hope is that the blue lights will be so effective,  active enforcement won’t be necessary long-term.

A blue light, positioned on each of the four corner intersection poles, turn on whenever the opposite signal light turns red.

“The comments we’ve received from local police is they don’t want to write tickets; they just want people to quit running red lights,” Lux said.

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Blue light indicators were affixed to existing signal poles at Lexington Avenue and Larpenteur Avenue in Roseville.

The blue light indicators allow a police officer to view an infraction from many viewpoints, instead of having to pursue the offending vehicle through the intersection. Also only one squad is required to patrol an intersection; not two.

The blue light indicators have been shown to increase traffic safety. In Florida, crashes due to people running red lights fell by 33 percent, according to a low-cost safety improvement pooled fund study conducted on behalf of MnDOT and 37 other states.

Unlike Florida’s blue lights, Ramsey County’s are being placed on the signal pole, instead of the masthead. They’re more prominent than a couple indicators the county tried previously at accident-prone intersections in Little Canada and Maplewood.

“They’re bright and noticeable to the public, but not distracting, like the ones Florida puts on the masthead,” Lux explained.

According to WCCO-TV, the blue lights are funded by a $120,000 federal grant, with $13,000 in matching local funds.

Temporary signs will be put up by Ramsey County to notify the public of the new indicators.

A few other Minnesota communities — including Blaine, Crystal, Olmsted County and Dakota County — have also installed blue light indicators in recent years.

Lux explained that Ramsey County is installing blue lights on intersections that are easily enforced by law enforcement, as well as those that aren’t, in hopes that the public will obey them all because of the heightened presence.

Bridges and Structures

Continuous Scour Monitoring Improves Bridge Safety

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A leading cause of bridge failure is bridge scour, which occurs when rapidly moving water erodes riverbed soil around abutments or piers.

Monitoring bridge scour with traditional inspection methods can be dangerous and difficult, so MnDOT has been working with researchers from the University of Minnesota’s St. Anthony Falls Laboratory to develop a continuous monitoring system to test certain bridges more safely and efficiently.

MnDOT currently monitors 45 scour-critical bridges — and local Minnesota agencies monitor 360 more — using visual inspections or water data websites during flooding events. Once a predetermined threshold is exceeded, portable scour monitoring equipment is deployed to measure scour depth.  If scour has undermined the foundations of a bridge, inspectors close it for repair.

But portable scour monitoring systems can be difficult and dangerous to deploy from the bridge deck or boat in fast-moving water. It can also be difficult to get inspectors to sites quickly enough in areas subject to flash flooding.

A better alternative for such situations are fixed scour monitoring devices that continuously monitor scour and send data wirelessly to bridge personnel, alerting them when scour reaches a dangerous level.

The Highway 43 Bridge in Winona was affixed with continuous bridge scour monitoring equipment.
The Highway 43 Bridge in Winona was affixed with continuous bridge scour monitoring equipment.
New technology

MnDOT has not historically made use of fixed scour monitoring equipment, but as advances in technology have made these devices more affordable and reliable, the agency  became interested in exploring the use of fixed monitoring equipment at locations where the use of portable equipment is problematic. ( A major concern for fixed scour monitoring is damage from debris and ice.)

Researchers have installed fixed remote monitoring stations on four such bridges.

Stations on the first two bridges (Highway 14 over the Minnesota River in Mankato and Highway 43 at the Mississippi River in Winona, pictured at top) ran successfully for three years, with outages due to primarily to power and communication issues.

Researchers learned valuable lessons from these bridges and have now installed monitoring equipment on two more: The Old Hastings Bridge (Highway 61 over the Mississippi River), on which float-outs were installed; and the Dresbach Bridge (Interstate-90 over the Mississippi River), which had a tilt meter and underwater sonar device installed.

“The less familiar personnel are with technical equipment, the less they tend to use it,” said Andrea Hendrickson, State Hydraulics Engineer, MnDOT Office of Bridges and Structures. “This research project gave us the familiarity and technical information we need to be comfortable using fixed scour monitoring equipment on bridges that warrant it.”

Related Resources

*Editor’s note: This article was adapted from an article in the latest issue of our newsletter, Accelerator. Read it online, or sign up to receive it by mail. 

Bridges and Structures

Video: Load Testing for the Winona bridge

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New video, below, shows how explosions are used to test the bedrock for the new Highway 43 bridge in Winona.

Bridge engineers use “pile load testing”  to find out how much weight and resistance the ground will bear. It not only saves time and money, but helps design a bridge that will sit securely on the bedrock, below the river.

The statnamic test used in the video is one part of this process.

Winona Bridge Statnamic Test

 

How load testing works: 

It begins with digging and pounding.

Two different kinds of piles are put into the ground:

  • A hollowed shaft, which is filled with rebar and concrete. It goes 30 to 50 feet below the bedrock to create a solid pillar that can assess how much weight and sway the ground will bear.
  • A steel pipe that is hammered into the ground. Since the bedrock is about 100 to 150 feet below the river, these pipes are welded together end-to-end to reach that length.

Once the piles are in, they’re tested two different ways.

  • Pile Dynamic Analysis, with gauges affixed to the top of the pile to read the pressure put on it when hit with a pile driver.
  •  A Statnamic test (shown in videos), which involves accelerating a heavy weight by setting off a controlled combustion reaction. This shows how much resistance the pile can take.

Once the data is collected for the bridge design, the piles are cut off two feet below the river bed.

Maintenance Operations

Mobile imagery, LiDAR help MnDOT maintain its assets

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How do you quickly and cost-effectively get an accurate inventory of transportation assets spread out along more than 1,100 miles of roadway?

That was the problem facing the Minnesota Department of Transportation’s Metro District, which needed an inventory of its plate beam guardrail and concrete barriers.

To accomplish this, engineers in the district launched an innovative research implementation project using a pair of mobile mapping technologies — Light Detection and Ranging (LiDAR) and mobile imaging — that can collect vast amounts of geospatial data on highway infrastructure in a safe and efficient manner.

Mobile imaging uses a camera mounted on a vehicle driving at highway speeds to take high-resolution photos at regular intervals. It’s accurate to within 1 foot, which makes it suitable for use in preliminary (30 percent) design plans without additional field surveys. In this project, researchers collected mobile images of roadway barriers and extracted data from them along Metro District roadways, including all ramps, overpasses, interchanges, weigh stations, rest areas and historical sites.

A MnDOT worker replaces a section of broken guardrail.
A MnDOT worker replaces a section of broken guardrail on I-94 near the Lowry Tunnel in Minneapolis. (Photo by Dave Gonzalez, MnDOT)

Researchers also collected LiDAR data at three Metro District sites. LiDAR uses a laser range finder and reflected laser light to measure distances. It provides survey-grade data accurate to within 0.1 foot, but it is significantly more expensive to collect than mobile imaging.

“Mobile imagery and mobile LiDAR are relatively new technologies, but this research shows that they are options that we can use. Collecting this information manually would have taken a lot more time and money,” said MnDOT Asset Management Engineer Trisha Stefanski.

MnDOT’s barrier inventory will provide invaluable information for design, planning and maintenance. The data will be published on MnDOT’s Georilla map server, where it will be beneficial to a variety of projects and recurring tasks. For example, if a vehicle hits a barrier, maintenance staff will be able to check the database to see the type of barrier and end treatment to ensure they bring the right equipment to make repairs. Although the project focused on barriers, the imagery contains data on other assets as well. MnDOT has already used the imagery to extract noise wall and sign data.

This blog post was adapted from an article in our upcoming issue of Accelerator, MnDOT’s research and innovation newsletter.

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Thousands of data points can be extracted from this image of a Highway 61 roadway segment created with LiDAR Technology.
Bridges and Structures

‘High Bridge’ study yields insights on bridge deck maintenance

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One of St. Paul’s most iconic landmarks is helping the Minnesota Department of Transportation find the most cost-effective methods of maintaining concrete bridge decks.

For the last three years, the Smith Avenue High Bridge, which connects downtown St. Paul with the city’s west side, has served as a test bed for a variety of products used to seal cracks on bridge decks. Through MnDOT-funded research, various sealant products have been applied on different areas of the bridge deck, with their performance tracked over time.

“This project will help MnDOT make cost-effective maintenance decisions to preserve its current bridge infrastructure,” said Sarah Sondag, a senior engineer with MnDOT Bridge Operations Support.

The bridge was chosen in part because of its large deck area, which allowed for the application of 12 sealant products and three control sections.

Sealing deck cracks is a routine preventive maintenance task for bridge crews. Left untreated, cracks can allow moisture and chlorides to penetrate the bridge deck, which can lead to the corrosion of reinforcing steel, deck deterioration and the need for early deck replacement.

researcher testing permeability of a deck crack on the Smith Avenue Bridge
A researcher tests the permeability of a crack on the deck of the Smith Avenue High Bridge in St. Paul.

MnDOT maintains a list of approved bridge deck crack sealing products, but until now had little data on how well each one performs in the field. The recently published report also examined several products that are not currently on the Approved Products List.

Among the study’s findings: some of the products on MnDOT’s Approved Products List did not perform as well as other products that are not currently on the list. MnDOT is using the results of the study to update its qualification process for products to get on the approved list. Insights gained from studying application techniques will also be used to update MnDOT’s bridge maintenance manual.

*Note: This blog post was adapted from an article and technical summary that will be featured in the upcoming issue of the Accelerator newsletter.

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