Bump Outs: A primer for roadway safety

A new quick-build, midblock Bump Out in Broadway Ave in Beechview that both shortens the distance for pedestrians to cross the street and provides safe access to the trolley stop. Once the design is finalized, these can be upgraded with more permanent materials.

Bump outs help all road users in ways that may not be obvious

The City of Pittsburgh’s Department of Mobility and Infrastructure (DOMI) has been installing Curb Extensions and/or “Bump Outs” to help add clarity to streets and to provide added safety for pedestrians at key locations. Bump outs are one tool that traffic engineers can use to “calm traffic” and increase safety along a corridor. 

What is a Bump Out and what do they do?

Basically, a bump out is created when a bit of an existing street or parking space is repurposed for other uses. Bump outs can take several forms, depending on context, budget, and speed in which they can be installed. Often the street surface remains, but sometimes the sidewalk surface is actually extended to fill the new space, effectively creating a larger sidewalk. The most common placement of a bump out is at the intersection, but they can also be placed midblock creating a pinch point to slow cars and reallocate the space to other uses. 

By extending and aligning the curb with parked cars, bump outs visually and physically narrowing the roadway, slowing cars down, and creating shorter crossings for pedestrians while increasing the available space for street furniture, bike share stations, plantings, and street trees. 

A quick-build bump out on Frankstown Ave in Larimer makes it clear where cars should drive and helps pedestrians cross the intersection

They have the added benefit of increasing the visibility of pedestrians who are waiting to cross a street. Additionally, bump outs can increase visibility at intersections and help drivers who are pulling out of cross streets by preventing cars from parking too close to the intersection and blocking the view (which is illegal).

On Smithfield St in Downtown, an extended curb allows for the installation of a bus shelter for waiting passengers and planters, as well as freeing up the sidewalk for pedestrians.

Bump outs are also useful at bus stops to create an area for buses to more easily pull up to the curb, while preventing cars from blocking the stop. These “bus bulbs” are especially important for transit riders who use the bus’ wheelchair ramp or who need the bus to kneel. They can also create additional space outside of the main sidewalk for transit riders to wait for a bus or to provide space for a shelter.

Finally, they can serve as a gateway of sorts to a neighborhood. By decreasing the overall width of the roadway, bump outs can serve as a visual cue to drivers that they are entering a neighborhood street or area.

This bump out on Walnut St in Shadyside clears up sidewalk space by providing bicycle parking, while also making it easier and safer for drivers to pull out of the side street with the increased visibility.

Bump Outs are becoming a common feature in the City’s traffic calming program and future Neighborways program. The City has been installing a large number of bump outs using flexible bollards. 

The benefits of using flexible bollards are that they are quick to build and allow them to monitor the installations and make changes, all without affecting drainage or spending very much money. The downside is that the bollards feel temporary, may even be seen as unsightly, and require regular maintenance and replacement. However, it may be easy enough to transform them into a more permanent installation when money becomes available.

The curb extensions at a bus stop on Liberty Ave in Downtown serve multiple purposes: shortens the crossing distance for pedestrians, creates a sitting area, adds space for landscaping, makes it easier for a bus pull to the curb, and even adds a place to eat take-out

In the right situation, Bump Outs are a versatile tool that traffic engineers can use to control speeds, provide space for pedestrians, prevent illegal parking, and add clarity to the street.

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