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Stroad (Commercial Arterial)

ART-STD-05
Avoid Arterial

Stroad (Commercial Arterial)

A street and Arterial hybrid, known under two common names, Stroad (coined by Strong Towns) and Commercial Arterial: through traffic mixed with on-street parking, frequent direct commercial driveway access, or both, along the same corridor.1 This is the exact combination the Arterial core safety rule prohibits: arterials should carry through traffic without direct property access or on-street parking competing for the same space.2

Occurs most often at: Rural Suburban Compact

Undeveloped and Urban are edge cases. Core is an unlikely pairing.

Avoid

Stroad is an explicit Avoid pattern within the Commonway System, not a Typology to design toward. No default modal order is assigned, since the pattern itself is the anti-pattern being flagged.

Speed and modal hierarchy

Design speed & speed limit

[SPEED LIMIT 40] [SPEED LIMIT 45] [SPEED LIMIT 55]
Stroad mixes through traffic with on-street parking and direct driveway access, the exact combination the Arterial core safety rule prohibits. No single design speed is safe for this mismatch; the signs above show the density-tiered baseline this pattern violates, not a speed to design toward.

See Design Speed & Speed Limits.

Modal hierarchy

No default modal order is assigned, since the pattern itself is the anti-pattern being flagged.

Illustration

Type: Single-condition. Format: Segment / cross-section (~2.8:1).

Typical condition
Mixed on-street parking and a through-traffic lane, with no protected crossing; the entire condition is amber-flooded, per the Single-condition rule for Avoid patterns.

Callouts

  1. (Physical) On-street parking beside through lanes.
  2. (Physical) No protected or signalized midblock crossing despite pedestrian-generating land use.

Instead, see: Boulevard (ART-BLV-02), Default Arterial (ART-DEF-01) + Frontage / Service Road (LOC-FSR-04)

Supplemental illustration, justified: the driveway-spacing claim below is longitudinal, and the required cross-section format above is lateral and can't show it.

Type: Supplemental (plan-view). Format: Wide (16:9 or wider).

Plan view
Direct driveway cuts spaced every 100–200 ft along the corridor, with no parallel frontage or service road to aggregate access points.

Callouts

  1. (Physical) Direct driveway cuts every 100–200 ft.3
  2. (Physical) No parallel frontage/service road to aggregate access points.

Related Media

The items below come from outside the Commonway System, external videos, podcasts, and articles related to this page's topic, not part of the guidebook itself.

Aligned

You've Been Lied To About Roads For 60 Years

Global Cycling Network

Covers "junk roads," traffic-model incentives to overbuild, and the trillion-dollar cost of designing roads around growth projections that the roads themselves inflate.

Aligned

More Lanes Are (Still) A Bad Thing

Not Just Bikes

Lays out induced demand, Braess's Paradox, and traffic evaporation with real case studies (LA 405, Houston Katy Freeway, Cheonggyecheon), then shows the Dutch one-lane-plus-transit cross-section as the actual fix.

Aligned

Stroads are Ugly, Expensive, and Dangerous

Not Just Bikes

The definitive explainer on stroads, and lays out the Dutch three-tier road/street classification system that CS's own Functional Classification structure closely mirrors.

Design notes

The density figures above track how often this pattern actually occurs in the built environment, not whether it should. It is most common from Rural through Compact density, matching the typical state-highway-turned-suburban-corridor problem: a road built for through movement that gradually accumulates driveways and curb cuts as adjacent land develops.

Every direct driveway or curb cut along the corridor is a conflict point undermining both through-traffic flow and safety: access-point density correlates directly with crash rate, with high-density segments running roughly three times the crash rate of well-managed comparison segments.3

This page exists to help readers identify a Stroad and replace it, with Boulevard where a pedestrian-first frontage fits the corridor, or with Default Arterial paired with a separate Local or Frontage/Service Road where it does not.

Boulevard (ART-BLV-02), Default (No Parking, No Direct Access) (ART-DEF-01), Frontage / Service Road (LOC-FSR-04)

References

  1. Precedent-based Marohn, C., "What's a STROAD and Why Does It Matter?", Strong Towns.
  2. Legal / regulatory American Association of State Highway and Transportation Officials, A Policy on Geometric Design of Highways and Streets ("Green Book").
  3. Evidence-based Gluck, J., Levinson, H.S., and Stover, V., Impacts of Access Management Techniques, NCHRP Report 420, Transportation Research Board, 1999. Crash rates rise consistently with access-point density; high-density segments show crash rates approximately 3x well-managed comparison segments.