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City Limits Index

City Limits
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CONFLICT DENSITY

CONFLICT DENSITY

Two primary factors determine how frequently potential conflicts between motor vehicles and people walking or bicycling arise on the street: Modal Mixing + Crossing Point Density = Conflict Density

MODAL MIXING

How much physical separation the street offers people walking, biking, and rolling along the street.

Typical modal separation patterns in urban contexts:

HIGH MODAL MIXING
(LITTLE OR NO SEPARATION)

> No sidewalks or sidewalks directly adjacent to moving motor vehicle traffic
> Bicycle traffic expected to use a mixed-traffic lane or a designated shared bike-motor vehicle lane (e.g., sharrows)

MODERATE MODAL MIXING
(MODERATE SEPARATION)

> Urban Street Design Guide (USDG)-compliant sidewalk, and/or a curbside loading/parking lane and sidewalk
> If designated as a bike route, a marked bike lane or better
> If not designated as a bike route, a full sidewalk that also permits bicycle use

LOW MODAL MIXING
(FULL SEPARATION)

> If designated as a bike route, a sidewalk compliant with the Urban Street Design Guide plus a vertically and horizontally protected bike lane, or a shared-use path/trail
> If not designated as a bike route, a full sidewalk that also legally permits bicycle use
> Passengers exiting parked or loading vehicles are not directly in motor vehicle traffic lanes

CROSSING POINT DENSITY

How closely spaced intersections and other crossing locations are.

Typical crossing point density patterns in urban contexts:

HIGH DENSITY OF CROSSING POINTS for bicyclists, pedestrians, and motor vehicles

> 3 or more “through” or “X” intersections (signalized or unsignalized), “T” intersections, driveways, curb cuts, or other crossing points per 1/4 mile

MODERATE DENSITY OF CROSSING POINTS for bicyclists, pedestrians, and motor vehicles

> 1-3 “through” or “X” intersections (signalized or unsignalized), “T” intersections, driveways, curb cuts, or other crossing points per 1/4 mile

LOW DENSITY OF CROSSING POINTS for bicyclists, pedestrians, and motor vehicles

> No “through” or “X” intersections (signalized or unsignalized), “T” intersections, driveways, curb cuts, or other crossing points per 1/4 mile

 

APPLYING A CONFLICT DENSITY ANALYSIS ON EXAMPLE STREETS

Example Street A

Minimal separation for cyclists: HIGH MODAL MIXING +  Short blocks: HIGH CROSSING POINT DENSITY = HIGH CONFLICT DENSITY

Example Street B

Minimal separation for cyclists: HIGH MODAL MIXING +  Short blocks: HIGH CROSSING POINT DENSITY = HIGH CONFLICT DENSITY

Example Street C

USDG-compliant sidewalk: MODERATE MODAL MIXING + Moderate length blocks: MODERATE CROSSING POINT DENSITY = MODERATE CONFLICT DENSITY

Example Street D

Full separation for cyclists and pedestrians on multi-use path: LOW MODAL MIXING + Very low demand for vehicular or pedestrian crossing: LOW CROSSING POINT DENSITY = LOW CONFLICT DENSITY

References