Alternate Roadway Design for Flexible Capacity

Roadway design had remained consistent for years. A lack of evolution lead to the inability to adjust to changing capacity, increased speeds, and technologically advanced vehicles. These new driving conditions have caused roadway congestion beyond what the existing system is capable of handling. Solutions such as overpasses and high occupancy vehicle lanes have been developed and implemented in areas of high traffic congestion however, we have yet to find a combination of roadway design pieces that adequately handle the problem at large. As roadway design evolves, we look to new solutions such as reversible lanes to solve these problems within the existing infrastructure as well as their benefits in newly redesigned systems. 

Managed lanes can be defined as lanes that use operational strategies to influence roadway usage¹. As seen in the graphic below, the Texas DOT uses lane management strategies that control access control, vehicle eligibility, and pricing to control how lanes are used. 

A graphic showing lane management strategies and their complexity. Source: Texas DOT

These lane management strategies work in different ways; toll lanes raise the cost of private transportation which incentivizes public transit use, HOV Lanes increase roadway capacity by increasing passenger density. Essentially, all of the lane management systems work to decrease the number of cars per lane on the roadway. Reversible lanes are specifically one of the most useful roadway design tools that are available today.

Reversible lanes are lanes that have the capability to change direction depending on the time of day. This flexibility can work to dissipate the issue of unbalanced directional distribution by increasing peak direction capacity². When roadways are designed, the capacity is meant to carry the peak amount which occurs during only a few hours of rush hour; this results in the overdesigning of roads that are unused to their capacity the majority of their existence and seemingly insufficient during the remaining time. During rush hour, the roadway is most often at capacity in only one direction leaving the other direction below capacity. By utilizing flexible lanes we can design our roads to a more appropriate size that will carry the same capacity with less impact.

An example of unused roadway capacity that could be utilized through the instillation of flexible lanes. Source: The RAC

Reversible lanes can be added into existing roadways. The extent of changes required depends on roadway capacity and speed. For situations with low speeds, adding paint lines and installing traffic lights to indicate roadway direction may be adequate. For areas with higher capacity and faster travel speeds, it may be necessary to move barrier rail, pave new lanes connecting opposite direction traffic, and replace barrier rail and movable traffic barriers. In either situation, the required changes are small in comparison to the benefits of the outcome. Reversible lanes are also beneficial when being considered in the original design process. As the flexibility given by the lanes is able to increase roadway capacity, less lanes will be required to achieve the same result in initial design. Fewer lanes result in less required right of way, less environmental impact, lower construction costs, and faster construction times.  

Reversible lanes offer many benefits, but as with any new system they pose potential issues as well. The equipment required for this system varies from traditionally used traffic control. Traffic direction lights have possibilities to malfunction and moving barricades could break or be damaged by traffic requiring downtime for repair. A slight increase in operating cost is not beneficial in addition to increased maintenance cost. Where money is saved in construction cost, some of it will be required to keep the system functioning properly. Furthermore, the physical roadway changes are not the only places where issues may occur. Drivers not educated on the functions of this system could cause safety issues for other drivers. It would be imperative to include proper signage and education when installing reversible lanes to prevent safety problems caused by users of the road.

Seeing the potential benefits and issues associated with reversible lanes brings about the question, are reversible lanes the roadway design of the future? State Departments of Transportation across The United States seem to think they are. Reversible roadways exist already in Arlington Tx and other cities across the U.S. and more large installations have been proposed in Colorado, Arizona, and more³.  As transportation conditions worldwide continue to change, the design of roadways will have to become even more flexible, innovative, and mindful. Reversible lanes are one of many tools that will allow roadways to be adaptable to an everchanging transportation system. 

1. “Managed Lanes” Texas DOT https://www.txdot.gov/driver/managed-lanes/managed-lanes.html
2. “The real causes of motorway traffic and how to stop it” RAC https://www.rac.co.uk/drive/advice/driving-advice/traffic-jams-what-causes-them/
3. “Reversible Traffic Lanes” Mobility TAMU https://mobility.tamu.edu/mip/strategies-pdfs/traffic-management/technical-summary/Reversible-Traffic-Lanes-4-Pg.pdf

Urban Transportation in the Twin Cities: A Regional Effort

Metro Transit Created to Address Regional Needs 

The Twin Cities Metropolitan Area covers over 8,000 square miles including the state capitol of Minnesota, St. Paul, and the larger city of Minneapolis, as well as suburbs in the surrounding seven counties.¹ In the 1960’s, the state determined that a regional approach would be the best way to coordinate transportation, as well as other regional-scale issues such as water treatment and open space. In 1967, the Minnesota legislature created a Metropolitan Council that oversees these services in the seven counties that they defined as the Twin Cities Metropolitan Area. Since then, urban transportation in the region has been transformed from private companies and individual cities to a comprehensive system of highways, bus lines, light rail, bike paths, and an airport all coordinated by the Metropolitan Council.¹

The Existing System 

 Metro Transit, the public transportation agency run by the Metropolitan Council, has a network that includes 130 routes, with service levels and type connected to land use patterns. Three of these along major commuting corridors are rail lines: Blue Line light rail, Green Line light rail, and Northstar commuter rail. Light rail was first proposed in the 1980’s but did not have enough support until 2004, when the Blue Line opened along a right-of-way in south Minneapolis originally obtained for a highway that was never built. After the Blue Line’s success, the Northstar heavy rail line opened for commuters living northwest of the Twin Cities in 2009 and the Green Line light rail connecting two major economic sectors, downtown Minneapolis and downtown St. Paul, was completed in 2014. These routes now make up approximately 32% of Metro Transit’s rides, while buses make up the remaining 68%.² Buses, arranged in a hierarchy of infrequent routes, peak routes that come every 10 to 15 minutes, and Bus Rapid Transit (BRT) lines, function as feeders to rail services as well as being the main routes in areas with lower housing and commercial density. 

Success and Future Challenges

Though there are issues with it, the Metro Transit system is fairly comprehensive. Its beginnings from the Metropolitan Council mean that the system was designed at a regional scale, rather than incrementally by individual city resources. The system covers 90 cities in the Twin Cities Metropolitan Area with varying levels of service, providing access to both suburbs and inner-city populations. The hierarchy of service options ensures cost-effective and user-friendly connectivity throughout the region. Additionally, using existing right-of-way and a pro-transit political climate helped the Metropolitan Council implement efficient, heavily used rail and BRT lines. High-frequency bus and light rail routes provide service in high-demand and densely developed areas, taking in 30% of all weekday riders despite being only 1% of the routes offered. The construction of rail and BRT lines along commuter corridors increased park-and-ride usage by 80%, indicating their success at attracting transit riders from low-density suburbs.² The Metropolitan Council’s coordination of Metro Transit routes, interstate highways, local streets, and even bike paths along open spaces helps to maintain an accessible and mobile Twin Cities transportation network. 

The state of urban transportation in the Twin Cities is informed by the area’s past but will face the challenges of its future. Projected population and economic growth in the Twin Cities Metropolitan Area will usher in new transportation concerns to connect people with jobs. By completing a Transportation Policy Plan through 2040, the Metropolitan Council is starting to address these issues.³ However, when these plans are carried out, they still need to address the public’s concerns of equity and sustainability. It remains to be seen how the new light rail and BRT lines will use existing resources to improve the accessibility and mobility of all within the region. 

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1. “History of the Metropolitan Council.” Metropolitan Council, metrocouncil.org/About-Us/What-We-Do/Metropolitan-Council-History.aspx. 
2. “Metro Transit 2018 Facts.” Metro Transit, 2018, http://www.metrotransit.org/metro-transit-facts. 
3. United States, “Thrive MSP: Transportation Policy Plan.” Thrive MSP: Transportation Policy Plan, Metropolitan Council, 2015. https://metrocouncil.org/Transportation/Planning-2/Key-Transportation-Planning-Documents/Transportation-Policy-Plan-(1)/The-Adopted-2040-TPP-(1).aspx. 
4. Mueller, Matthew. “Equity of Transit in the Twin Cities: a Benefit-Based Study of the Racial Equity of Access to Transit.” Columbia University, 2014, https://academiccommons.columbia.edu/doi/10.7916/D8PZ5H6P/download
5. Regan, Sheila. “What Light Rail Will Mean for Property Values.” Southwest Journal, 23 Sept. 2019, http://www.southwestjournal.com/focus/real-estate/2019/09/what-light-rail-will-mean-for-property-values/
6. “Transit Improvements.” Metro Transit, 2019, http://www.metrotransit.org/transit-improvements.