3-4 Travel Lanes

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Travel Lanes Travel lane design depends on available right-of-way, land use context, user mix, traffic volumes, and roadway design speeds. Potential users include bicyclists and drivers of passenger cars, heavy trucks, and buses and emergency vehicles. Accommodating these modes is challenging within Boston’s constrained rights of ways.

As discussed previously, the number and width of motor vehicle lanes will be minimized to discourage speeding, provide space for pedestrian and bicycle facilities, and decrease impervious surface. Providing for truck traffic to industrial areas is necessary for economic development.

The design treatments on the following pages should be applied based on engineering judgment and in consultation with BTD. The guidance in this document should be supplemented with design guidance provided in the Manual on Uniform Traffic Control Devices, the MassDOT Project Development and Design Guide, and AASHTO Greenbook.

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More design guidance on specific travel lanes is provided on the following pages.

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Three Lanes with Center Turn Lane . . . . . . . . . . . . . . . . . . .

Peak Time Restricted Parking . . . . . . . . . . . . . . . . . . . . . . .

Routes Frequested by Heavy Vehicles. . . . . . . . . . . . . . . . .

Fire Department & EMS Accommodations . . . . . . . . . . . . .

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Three Lanes with Center Turn Lane

Shared Streets Neighborhood Connector Boulevard Parkway

Neighborhood Residential Neighborhood Main Street Downtown Commercial Downtown Mixed-use Industrial

Overview The most common road diet configuration in Boston involves converting a four-lane road to three lanes, two travel lanes with a two-way left turn lane (TWLTL) down the center of the roadway. If considered during a reconstruction, the median may be raised at locations to provide improved pedestrian crossings and opportunities for increased greenscape. This configuration: >> Discourages speeding, especially aggressive speeding and weaving >> Reduces the potential for rear end collisions >> Improves sight distances for left-turning vehicles >> Increases distance from fixed objects on the side of the road

>> Reduces pedestrian exposure to motor vehicle traffic >> Creates space for sidewalks, bicycle lanes, bicycle tracks, bus bulbs, or curbside parking >> Improves access for emergency vehicles, which can used the center turn lane to bypass through traffic Four to three lane conversions have been found to reduce total crashes by an average of six percent (as documented in the Highway Safety Information System). The magnitude of the safety benefit at specific location depends on the roadway context and the specific design of the conversion.

10 feet is the typical width

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of a center turn lane.

Use >> Four lane to three lane conversions should be considered for roadways with the following characteristics: >> Moderate volumes (8,000-15,000 ADT, up to 20,000 ADT in special cases) >> Documented safety concerns >> Priority bicycle routes >> Four to three lane conversions have minimal effects on the vehicular capacity of the roadway, because left-turning vehicles are moved into a common two-way left turn lane.

However, lane conversions on higher volume roadways (more than 20,000 ADT) should be studied carefully to ensure that traffic controls and access management are appropriate for larger volumes of traffic.

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>> The center turn lane can be 10’ wide in most locations. See minimum lane width chart for more information.

Considerations >> The space occupied by the TWLTL in the standard four to three lane conversion can also serve as a center island if site conditions warrant. Medians can be designed with left turn pockets and should provide pedestrian refuges at pedestrian crossing locations.

UPDATED AS OF December 2010

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Peak Time Restricted Parking Lanes

Neighborhood Residential Neighborhood Main Street Downtown Commercial Downtown Mixed-use Industrial

Overview

Use

Peak time restricted parking lanes are parking lanes that are converted to other uses during peak or rush hour times. The traditional application of this treatment involves converting parking lanes to general purpose travel lanes. However, peak time restricted parking lanes can also be converted to other purposes, including HOV lanes, bus lanes, and bicycle lanes.

>> Peak time restricted parking lanes may be considered on roadways where additional capacity is needed during peak hour. >> The decision to install peak time restricted parking must be accompanied by a prompt and rigorous enforcement effort that involves not only ticketing illegally parked vehicles but also towing them. mini>> Peak hour restricted parking lanes should be a mum of 12’ wide to accommodate shared use by parked cars and bicycles in off-peak times. See minimum lane width chart for more information (p. TK).

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Peak time restricted parking lanes can increase the capacity of the roadway for general purpose traffic. Depending on conditions, an additional travel lane can improve capacity by 600-1000 vehicles per hour. However, the capacity advantages of peak time restricted parking lanes for general purpose traffic assume universal compliance with the parking restriction. Illegally parked vehicles diminish these advantages and, if they happen with sufficient regularity, may eliminate them entirely.

Shared Streets Neighborhood Connector Boulevard Parkway

Considerations >> Converting parking lanes to general purpose travel lanes at peak times can make it difficult to accommodate bicycles along a roadway segment due to safety concerns associated with having moving traffic on both sides of a bicycle lane. A potential solution is to create a cycle track. >> In some situations, there may be benefits to removing peak time restricted parking lanes where they currently exist. The availability of parking during peak may encourage motorists to visit roadside businesses. Also, parking improves pedestrian comfort and safety by providing a

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buffer between pedestrians and moving vehicles. Finally, parking space that is not peak time restricted may be converted to other purposes, such as bus bulbs to improve transit efficiency. >> Peak time restricted parking lanes are not compatible with curb extension or neckdowns.

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Routes with Frequent Heavy Vehicles

Neighborhood Residential Neighborhood Main Street Downtown Commercial Downtown Mixed-use Industrial

Overview

Use

Many of Boston’s busiest streets are also frequented by heavy vehicles, such as buses and heavy trucks. Heavy vehicles have different performance characteristics than cars.

For example, they require more space for turning and more distance to stop. Therefore, it is important to ensure that roads frequented by heavy vehicles are designed to accommodate them safely alongside other roadway users.

>> Roadways with more than 8% heavy vehicles should 11’ outside lanes. generally have >> Intersections should be designed with turning radii and stacking space sufficient to accommodate heavy vehicles (more guidance is provided in Chapter 4: Intersections). >> Heavy vehicle braking characteristics should be considered when determining the placement of warning signs for intersections, curves, railroad crossings, mid-block pedestrian crossings, and shared-use trail crossings. >> Separate cycle tracks or side paths should be provided on heavily used routes if insufficient space is available in the roadway to accommodate both heavy vehicles and bicyclists safely. >> Skid resistance and strength should be considered when choosing pavement surfaces for routes frequented by heavy vehicles (See High Impact Roadway Materials).

Wider travel lanes, typically 11 feet, are appropriate on roadways frequented by heavy vehicles.

Shared Streets Neighborhood Connector Boulevard Parkway

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In areas frequented by heavy vehicles, such as Industrial Streets, pedestrian and accessibility accommodations are necessary.

Considerations >> Flush medians or center turn lanes of sufficient width can help facilitate left-turn movements for heavy vehicles by providing a space to stop and wait for gaps. >> On sharply curving roads frequented by heavy vehicles additional lane width may be necessary.

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Fire Department & EMS Accommodations

Neighborhood Residential Neighborhood Main Street Downtown Commercial Downtown Mixed-use Industrial

Shared Streets Neighborhood Connector Boulevard Parkway

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In development.

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