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.
|Safe street design tools
|Why SASS backs it
|Pedestrian refuge island / Median island
|Slows 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.
|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.
|Raised crosswalks (and where present, crossbikes) at all side street crossings
|More 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
|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.
|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.
|Gives vehicles, people on foot, and people on bikes their own safe spaces at intersections (reduces conflict), reduces traffic turning speeds, improves sightlines
|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.
|Wide, high-visibility crosswalks
|Recognizable, 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
|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.
|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.
|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.
|Quality bus stops that include shelters, benches, trash cans, appropriate sidewalk width
|Accessible 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.
|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.
|Accessible and smooth brick alternative walkway materials such as stamped concrete
|Smooth 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.
|Properly Designed Crosswalk Lighting
|Crosswalks 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.
|Mini Roundabout and Neighbor- hood Traffic Circle
|Mini 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: http://tacticalurbanismguide.com/
SASS-opposed existing conditions or design tools
“Eliminate these whenever possible and do not add any more in Somerville”
|Condition or tool opposed by SASS
|Conventional all-brick sidewalks and paths
|Tripping and accessibility hazard, especially over time; more accessible alternatives like stamped concrete exist
|ADA-violating cross-slope where sidewalks cross driveways or parking lot entrances
|Wheelchair 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 obstructions
|Danger to all pedestrians, especially to children and people in wheelchairs
|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 signs
|Affects 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)
|Unnecessary for movement, enable high speeds that endanger people walking
|Blind left turns
|Lack of visibility with no control over cross traffic is unsafe (example: Quincy Street approaching Summer Street)
|HAWK (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 lanes
|Bumpouts 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 red
|Allowing 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 direction
|Multiple 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.