I-495 & I-270 Managed Lanes Study
Six screening criteria were used to evaluate, screen, and refine the Preliminary Range of Alternatives to the seven Screened Alternatives. These criteria were based on the transportation needs and goals outlined in the Study’s Purpose and Need and applied to each alternative:
- Accommodating existing traffic and long-term traffic growth
- Enhancing travel time reliability
- Providing additional travel choice while retaining the general-purpose lanes
- Evaluating complex operating configurations that lead to driver confusion
- Accommodating Homeland Security by providing additional capacity to assist in accommodating population evacuation and the ability to quickly coordinate a traffic response by allowing use by emergency responders
Movement of Goods and Services
- Improving movement of goods via truck freight travel and enhancing the movement of services by improving access to employment centers
- Improving multi-modal connectivity by enhancing connections to and between existing transit facilities near the corridor and accommodating new or modified transit service with the alternative.
- Addressing financial viability
- Consideration of key environmental resources that require additional property and impacts to parks, historic properties, and wetlands and waters
MDOT SHA has carried forward Alternatives 1, 5, 8, 9, 10, 13B, and 13C for further analysis and environmental evaluation. All alternatives, other than the No Build, include managed lanes, either High Occupancy Toll Lanes also known as HOT lanes or Express Toll Lanes also known as ETLs, and combine congestion pricing and lane management to control the number of vehicles entering the lane to keep traffic flowing.
HOT Lanes and Express Toll Lanes provide people with a choice for a faster, predictable trip when they need it. ETLs require all users to pay a toll whereas HOT lanes provide reduced tolls for vehicles with multiple people in them. Toll rates are based on real-time traffic conditions. Every few minutes, the traffic management computer system updates toll rates based on how many vehicles are in the lanes and how fast they are going. Essentially, congestion pricing uses the laws of supply and demand to keep traffic moving.
When traffic is flowing smoothly and there is plenty of room in the HOT or ETLs, the price is low to encourage cars to get in. When the HOT or ETLs start to fill up and slow down, the price goes up in order to discourage too many cars from getting in so that the lanes can keep flowing efficiently. One of the benefits of HOT or ETLs is that they are designed to be more efficient than general purpose lanes when traffic is at its worst. At the height of the peak commute hours, ideally each HOT or ETL moves more vehicles than the general purpose lanes, which helps the entire highway flow more smoothly.
When drivers choose to leave the general purpose lanes to use the HOT or ETLs, they free up space for the other drivers around them. As a result, the general purpose lanes can move faster than they did before the HOT or ETLs opened.
The seven alternatives shown in the table below were carried forward for detailed traffic, environmental, and financial analyses to determine each alternative’s effectiveness at meeting the Study’s Purpose and Need. Although Alternative 1 does not meet the Study’s Purpose and Need, it was carried forward for baseline comparison purposes in accordance with the National Environmental Policy Act (NEPA).
Please view the Screened Alternatives video for a detailed explanation regarding how and why some alternatives were dropped from further consideration and others were carried forward as the Screened Alternatives. The video is approximately 17 minutes long. The seven Screened Alternatives are shown below.
Click each alternative in the chart below to view artistic renderings and descriptions that show how the build could work.
During Fall 2018 and Winter 2019, further technical studies were completed to determine the traffic operations, financial viability, and potential effects to environmental resources.
To view the typical sections of each of the Screened Alternatives, click here.
Alternatives Dropped from Further Consideration
The following alternatives were dropped from further consideration because they did not meet the screening criteria established by the Study’s Purpose and Need.
The Transportation System Management and Transportation Demand Management alternative (Alternative 2) would improve the operations of the existing transportation system. Benefits of these types of solutions optimize the existing system but do not support long-term traffic growth. For example, solutions of this type are currently under construction on 270. While these improvements are projected to provide an improved trip for the near future, the operations are expected to return to existing levels of congestion by 2040. These types of improvements would not enhance trip reliability, would not provide an additional travel choice, would not accommodate Homeland Security or improve the movement of goods and services, nor would it provide a revenue source.
High Occupancy Vehicle lanes or HOV lanes are only open to vehicles with a minimum number of occupants. Alternatives with only HOV lanes were Alternatives 4 and 7. They are being recommended to be dropped from further consideration because they would not support long-term traffic growth, would not ensure reliable trips on I-495 and I-270, and would not provide a revenue source. Even if MDOT SHA could fund this construction by using its entire budget for expanding the statewide transportation system, which is currently budgeted at $1.4 billion over the next six years, it would take more than 10 years to construct one HOV lane and 20 years for two-lane HOV lanes.
General Purpose Lanes are the lanes on a freeway that are open to all motor vehicles. Alternatives that only provide general purpose lanes are Alternatives 3 and 6. They are being recommended to be dropped from further consideration because adding one general purpose lane in each direction would not meet the long-term traffic demand. Adding two general purpose lanes in each direction would not provide a reliable trip because there would be no ability to manage the long-term demand to ensure it would not exceed the new capacity and result in breakdown conditions. Without being able to manage the lanes, an additional travel choice would not be provided. Additionally, General Purpose lanes would not provide a revenue source and, similar to HOV lanes, they could not be delivered for more than one or two decades.
Collector-Distributor lane systems (or C-D systems) (Alternative 11) physically separate local traffic entering/exiting at the interchanges from the long-distance or express lanes, which helps to reduce the number of conflicts on the highway. A C-D system works well on highways where there is a substantial volume of long-, medium-, and short-distance trips that could benefit from being separated from local trips. This type of system would not be favorable for the travel along 495 because it includes a mix of long, medium, and short-distance trips. Additionally, due to the high volume of traffic entering and exiting 495 at the interchanges, it would likely cause more congestion in the local lanes. Additionally, this type of system on 495 would require more widening to construct and would not provide additional travel choices nor a revenue source for the improvement.
Contraflow Lanes (Alternative 12A) are managed lanes operating on the opposite side of the median barrier, in the opposite direction of the flow of traffic. They are used to support heavy traffic in the peak-direction of travel and is separated by a movable barrier. Reversible Lanes (Alternative 13A) are designed to change the direction of traffic flow at different times of the day to match the peak direction of travel.
These types of alternatives are more effective where there is a significant directional split in traffic. For example, when the majority of traffic is moving in one direction in the morning and in the opposite direction in the evening. On I-495, traffic is fairly even by direction and peak period, so contraflow and reversible lanes would not provide additional capacity in the opposite direction of the contraflow or reversible lane, and therefore, these alternatives would not address long-term traffic growth in both directions simultaneously. Additionally, these alternatives would not provide evacuation options or improve freight travel. There is also no readily available revenue source for development of the contraflow lane improvements, so it is not likely to be financially self-sufficient.
Like I-495, contraflow lanes could be added on I-270, but MDOT SHA is recommending dropping Alternative 12B from further consideration because adding contraflow lanes on I-270 would mean that 1 lane would need to be removed in the off-peak direction (for example, removing a lane in the northbound direction during the morning peak period). Consequently, traffic would be required to cross over the highway median, which means that non-HOV users would have to merge into/across the existing HOV lane to enter and exit the contraflow lane, potentially impacting the operations and enforcement of these lanes approaching the contraflow access points.
Additionally, a movable barrier would be needed to separate opposing traffic. Shifting the barriers to provide the contraflow lanes for more than 10 miles of highway would take hours to complete, which reduces the roadway capacity during these times. Therefore, Alternative 12B is being recommended to be dropped from further consideration because it would only provide capacity in one direction, would not provide evacuation options, would not improve freight travel, would not enhance access to employment centers or existing transit, and would not include a revenue source for development of the improvements.
Transit-only alternatives (Alternatives 14A, 14B, 14C, and 15) could include heavy rail, light rail, bus rapid transit, and dedicated bus-only managed lanes. Based on feedback from you, we know providing transit options are important. The good news is that transit solutions are part of the overall traffic relief plan. There are a few reasons why stand-alone transit alternatives are recommended to be dropped. Overall, transit alone would not address the existing and long-term traffic growth in the study corridors. According to the National Capital Region Transportation Planning Board (or TPB), transit alone will not address the existing and long-term growth in the region. Both highway and transit options that complement each other are needed. For example, the Purple Line, currently under construction, will provide a great transit travel choice but significant congestion will still exist on 495 parallel to the Purple Line once it is opened for service. Additionally, stand-alone transit alternatives would not be financially self-sufficient. Therefore, stand-alone transit alternatives are being recommended to be dropped from further consideration. Bus usage, including consideration of additional express bus service as recommended by the TPB, will be examined in all ETL and HOT managed lanes alternatives to accommodate transit within the 495 and 270 roadways. In summary, this Study addresses highway improvements. MDOT has committed to working with the Washington Area Bus Transformation Project to incorporate results of that separate project to identify bus transit improvements for 495 and 270.