Safe Streets Guide

Commonly supported safe street design tools
That we want to see everywhere in Somerville

We recognize that achieving all of these principles can be challenging in constrained projects, but we believe these should be the bar for all future streetscape projects. This guide is a living document that SASS will update from time to time based on broad safe street advocacy input.

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Safe street design toolsWhy SASS backs itRepresentative pictures
Pedestrian refuge island / Median islandSlows turning traffic at intersections; makes turning vehicles more predictable by limiting where they can drive over the crosswalks; protects people walking with enough space to allow them to comfortably wait while crossing a street in two stages; can work well with bike and bus lanes
Preferable to bump outs on streets with two or more total travel lanes in any direction. Where built on streets without adequate bike lanes or bus lanes, ensure adequate width or flexibility for future improvements.
People walking and biking along a crosswalk with a refuge island on a two-lane road.Raised crossing with pedestrian refuge islands between opposite direction travel lanes.Diagram of a pedestrian refuge island as part of a crosswalk spanning lanes of motor vehicle traffic and bike lanes.
Speed humps and speed cushions (humps with fire truck/bus as well as bike wheel cutouts)Meaningfully slow down motor vehicles to safer speeds (15 mph) for people walking and biking. Speed cushions can work on major streets without causing bus or bicycle riders to suffer a bumpy ride. Work year-round, are permanent, and don’t depend on there being enough cars on the road to do their job.Example of a speed hump with a cutout in each direction for bike wheels.Example of a speed hump with wheel cutouts for an approaching bus. 
Raised crosswalks (and where present, crossbikes) at all side street crossingsMore accessible than up/down ramps (especially in winter snow), slow down turning traffic, increase visibility of pedestrians, and reinforce that people walking have the right of way.
Preferable to: Up/down ramps
Example of a raised crosswalk with adjacent raised bike path crossing.Example of raised crosswalk.Diagram of a 2 lane raised crosswalk that includes a raised bike crossing and adjacent speed humps.Diagram of motorist approach to a 2 lane raised crosswalk that includes a raised bike crossing
Separated bike lanes (also called  protected bike lanes)Give people on bike a safe space that keeps cars out with durable separation (not just paint and flexposts) so that people on bikes don’t need to seek refuge on sidewalks with associated bike-ped conflict; calms traffic by narrowing the car portion of roadway; makes crossing streets as a pedestrian more predictable because one knows where to expect cars and where to expect bikes. Integrates with accessible parking spaces.
Preferable to: Sharrows, painted “door zone” bike lanes.
Example of separated, or protected, bike lane.Another example of a separated, or protected, bike lane situated between a parking lane with accessible parking space with a buffer zone and the sidewalk.Example of separated, or protected, bike lane, with a marked crossing for a wheelchair user (leading to accessible parking space).Illustration of a separated, or protected, bike lane, adjacent to a travel lane, and with a marked crossing for a wheelchair user. From San Francisco Walks Guide.Illustration of a separated, or protected, bike lane, with a buffer zone between the lane and a parking lane.Example of a separated, or protected bike lane between a sidewalk and a railing-separated bus stop.
In-lane bus stops (also called bus bulbs)Buses can pull up completely to the curb, making access easier and safer for PWD, children, and all transit riders; makes buses run faster because they don’t have to reenter traffic; works with bus and bike lanes (behind the bus stop)
Preferable to: Straight-curbed bus stops at which buses must pull out of traffic to curb. 
Example of an in-lane bus stop (also called a bus bulb) with protected bike lane.Example of an in-lane bus stop (also called a bus bulb).Example of an in-lane bus stop (also called a bus bulb) with protected bike lane.
Protected intersectionsGives vehicles, people on foot, and people on bikes their own safe spaces at intersections (reduces conflict), reduces traffic turning speeds, improves sightlinesDiagram of a protected intersection.Illustration of a protected intersection.Diagram of a protected intersection showing bicycle and motorist travel paths.
Concurrent automatic crosswalk signals with leading pedestrian and bicycle intervals (LPIs) at most intersections (at least 5 seconds of head start)
At certain high-traffic intersections, add an automatic all-walk phase in addition to concurrent with LPI.
Gives all people walking (and where bike signals exist, people biking) a head start and gives people frequent chances to safely and legally cross the street, ideally no more than 30 seconds to wait for a walk signal in either direction; no pushing a beg button that may not work or be sanitary.
Where turning volumes are high, combine with raised crosswalks or raised intersections to slow turning traffic and increase pedestrian (especially child) visibility.
Example of a leading pedestrian interval (LPI) on a crosswalk signal.
Wide, high-visibility crosswalksRecognizable, easy for drivers to see, remains accessible because no brick pavers will fall out over time
Preferable to: Decorative brick crosswalks, parallel line painted crosswalks
Additionally: Incorporate bollards, jersey barriers, or other physical protection from vehicles and where it does not impede pedestrian travel
Example of a wide, high-visibility crosswalk.
Street tree bumpouts and sidewalks that bump out around large sidewalk trees instead of creating inaccessible pinch points, while providing green infrastructure allowing stormwater to drain into a rain garden and infiltrate the soil
Permeable flexible pavement to maximize clear width where there is already enough clear width without constructing a tree bumpout
Accessibility for wheelchairs, strollers; priority for people walking over private vehicle storage while growing the tree canopy; stormwater management through green infrastructure, especially where curbside parking is already not permitted; healthier, larger trees that do not block sightlines at intersections.
Low vegetation bumpouts at fire hydrants both improve stormwater management and fire department access, by preventing illegal parking.
Example of a street tree bumpout.Example of permeable flexible pavement to maximize sidewalk width next to street trees.Diagram of two curb openings allowing stormwater to drain into street trees and infiltrate the soil.Example of a street tree bumpout.Example of a street tree surrounded by a permeable surface.
Daylighting (providing safe, open sightlines at) intersections to at least the currently required 20 feet (without precluding bus or bike lanes)People on foot can see vehicles coming when they cross; eliminate dangerous blind spots at intersections. 
Can combine well with green infrastructure like bioswales.
Diagram of an intersection before and after the addition of daylighting.Example of daylighting applied in the layout of an intersection.
Bus priority infrastructure including: bus lanes, queue jumps, TSP (transit signal priority)Buses run faster, more reliably and potentially more frequently. Riders get where they’re going efficiently and with dignity instead of being stuck behind single-occupancy vehicles.Example of a shared bus priority and bike lane.shared bus priority and bike lanDiagram of a bus priority lane at the approach to an intersectionExample of a bus priority traffic signal.
Quality bus stops that include shelters, benches, trash cans, appropriate sidewalk widthAccessible and comfortable to wait at. Including to allow users past and to board/unload from the bus, and that are fully and quickly cleared of snow in the winter. Maybe also include more fun things like art.Example of a sheltered bus stop with seating, can accommodate many waiting riders comfortably.Illustration of a sheltered bus stop at an in-lane bus stop (bus bulb).Example of a sheltered bus stop with seating, incorporated into the street-facing facade of a commercial building.
Green and subsurface infrastructure: bioretention areas are similar to rain gardens, but are more highly engineered to include an underdrain, overflow inlet, gravel bed, and engineered soils to promote infiltration. (Mass DEP Clean Water Toolkit); Fixing gas leaks; Address climate change, tree health, air quality and public health, flooding prevention and mitigation, addressing subsurface priorities every time a street is opened up.
As of 2019, there were 168 identified and unrepaired gas leaks in Somerville. (Source: HEET) Gas is a potent greenhouse gas, is explosive and dangerous, and it kills street trees when it satures the soil. Photo below taken in East Somerville, in July 2019.
Diagram of bioretention subsurface infrastructure integrated below a street with various features such as a bike lane, an inline bus stop with street trees, and sidewalk.Illustration of a rain garden with a street tree.A 2019 map of 168 identified and unrepaired gas leaks in Somerville. (Source: HEET)Photo taken in East Somerville, July 2019, calling attention to the 168 identified and unrepaired gas leaks in Somerville.
Accessible and smooth brick alternative walkway materials such as stamped concreteSmooth and long-lived, without the accessibility and tripping dangers of conventional and even wire-cut bricks that fall out, heave from tree roots, and otherwise deteriorate.
Also: continuous tactile pavement features along walkways for people with visual impairment.
Accessible and smooth brick alternative walkway materialStamped concrete that looks like brick
Properly Designed Crosswalk LightingCrosswalks should be well lit at night for the entire length so that motorists can see and safely stop for people entering or in the crosswalk. A single overhead light above the crosswalk does not adequately illuminate the pedestrian for the approaching motorist. A FHWA-funded study found that 20 lx (a unit of illuminance) at a height of 1.5 m (5 feet) was necessary for motorists to detect a pedestrian in a midblock crosswalk. To achieve 20 lx, the luminaire should be placed 10 feet before the crosswalk, in between the approaching vehicles and the crosswalk. At intersections, the luminaires should similarly be placed before, not above or behind, each crosswalk.Schematic of Properly Designed Crosswalk Lighting with lights positioned before the crosswalk to illuminate pedestrians to motorists.
Mini Roundabout and Neighbor- hood Traffic CircleMini roundabouts can lower speeds at neighborhood intersection crossings that do not have all-way stops or traffic signals; neighborhood traffic circles can do the same at two-way or all-way stop intersections. Crashes are less frequent and less severe in these small circular intersections than in signalized intersections.Fuel consumption and vehicle emissions from idling are reduced with mini-roundabouts where everyone yields on entering.Shrubs or trees in the mini roundabout can increase traffic calming and beautify the street.

Quick-build versions of the SASS toolkit for immediate safety improvements

“Roll these out to calm speeding traffic and save lives within days or weeks, not months or years”

  • Pedestrian refuge islands (paint, flexposts, modular, rubber bumps)
  • Speed humps/cushions (rubber or asphalt)
  • Protected bike lanes and protected intersections (paint, flexposts, cones, plastic or concrete barriers, granite blocks)
  • In-lane bus stop (modular platform or asphalt)
  • Wide, high-visibility crosswalks
  • Crosswalk and intersection daylighting, including bumpouts (paint, flexposts, cones, bike corrals, granite blocks)
  • Bus lanes (paint, flexposts, plastic or concrete barriers)

Detailed reference: 

SASS-opposed existing conditions or design tools

“Eliminate these whenever possible and do not add any more in Somerville”

Condition or tool opposed by SASSWhy
Conventional all-brick sidewalks and pathsTripping and accessibility hazard, especially over time; more accessible alternatives like stamped concrete exist
ADA-violating cross-slope where sidewalks cross driveways or parking lot entrancesWheelchair users and strollers can be dangerously rolled down toward and into the roadway
Blind driveways with no way to see cars backing out due to fences, hedges, or other visual obstructionsDanger to all pedestrians, especially to children and people in wheelchairs
Blind driveway example with no way to see cars backing out due to fenceBlind driveway example with no way to see cars backing out due to a tall retaining wall constructed at a right angle and up to the sidewalk
Brick and paver crosswalks (like on Somerville Ave, in Davis Square, etc.)Tripping and accessibility hazard, especially over time as it disintegrates
Beg buttons (pedestrian crosswalk push buttons)They don’t reliably work, they require touching an unsanitary button, and they increase wait time to cross; not fair relative to motorists who don’t have to press anything.
Flashing LED lights on Stop signsAffects people with disabilities who cannot look at bright flashing lights.
At places where such lights have been installed, the City should investigate the need for installing speed humps or other traffic calming solutions instead.
Bike lanes dropping people into “sharrows”Dangerous; promotes bike-pedestrian conflict as people on bikes seek refuge on sidewalks; Somerville should prioritize pedestrian and bicyclist  safety over motorist convenience (parking lanes, extra driving lanes)
Slip lanesUnnecessary for movement, enable high speeds that endanger people walking
Blind left turnsLack of visibility with no control over cross traffic is unsafe (example: Quincy Street approaching Summer Street)
HAWK SignalsHAWK (High-Intensity Activated crossWalK) beacons are confusing and dangerous in an urban environment. The light phasing and overhead light positioning draws drivers’ attention away from visual checks for pedestrians in the crosswalk. At the same time, the pedestrian “walk” indicator gives pedestrians an unjustified sense of security. One of Somerville’s recent pedestrian fatalities occurred at the HAWK signal on Mystic Ave.
Bumpouts on streets that SBAC / PTAC identify as likely candidates for bike lanes or bus lanesBumpouts may preclude future safety features on a street, like protected bike and bus lanes. The same safety goals that bumpouts achieve can be achieved with pedestrian safety islands or other traffic calming measures.
Turns on redAllowing turns on red compromises pedestrian safety, undermines the headstart people get from a leading pedestrian interval, and encourages drivers to roll through red lights without coming to a complete stop. Somerville should install No Turn on Red (Except Bikes) signs by default at signalized intersections.
Multiple lanes in same directionMultiple lanes encourage speeding and create multiple threats for people crossing those lanes when traffic in one lane stops but the traffic in the adjacent lane does not. Multi-lane one-way streets and multiple lanes in the same direction should be eliminated in Somerville.