Peter G Furth Zhao Sha Sara Rauwolf Northeastern University Bike Lanes and Informal Flares: Making Longwood Avenue Safe and Functional for All Users Peter G Furth Zhao Sha Sara Rauwolf Northeastern University

On Longwood Ave, Are Bicyclists Intended* and Valued Users? Historical answer? “No.” Modern answer? “Of course!” Road layout’s answer? “I’m historical.” * As opposed to merely tolerated

Longwood Ave’s 32 Foot Constraint Car-Bus lanes: 10 to 11 ft Bike lanes: 4 to 6 ft So if cars “need” 2 thru lanes plus a left turn lane … At Brookline Ave eastbound each cycle: 2 cars turn left 10 bikes So why a left turn lane, but no bike lane???

Left Turn Lanes: Not for the Left-Turning Cars, but for the Other Cars!

Informal Flares: Preventing Blockage without a Left-Turn Lane Longwood Ave. @ St Paul Street, Brookline

Bike Lanes Can Help Create an Informal Flare St Alphonsus Street @ Tremont St, Boston

18 Ft Makes an Informal Flare With a 32 ft constraint: 4’ 10’ 12’ 6’

Traffic Simulation Demonstrates Feasibility Weekday, A.M. Peak Hour Volumes No change to boundary traffic signals (Riverway, Huntington Ave.) Uses VISSIM microsimulation software See the simulation

Is It Safe for Bikes? Cars enter bike lanes routinely Right turns Parking Getting around left-turning cars Line makes lane-changing right of way unambiguous and therefore safer

What the Highway Capacity Manual Says about Informal Flares [nothing] Options using Synchro* to account for informal flares: Model it as a short, narrow left turn lane There will be ample capacity if there are only a few left-turning cars per cycle) Ignore it Blockage caused by left-turning cars results in a capacity disaster * Best known software for intersection capacity, based on Highway Capacity Manual’s macroscopic formulas

With bike lanes sized to serve as informal flares, it’s possible. Making Longwood Avenue Safe and Functional for All Intended Users With bike lanes sized to serve as informal flares, it’s possible.

Why Mixed Traffic Doesn’t Work Green light: Cars need to pass bikes Cars & bikes single file would be a capacity disaster Red Light: Bikes need to pass cars Bikes need to be advance to the head of the queue in order to be visible & safe