Street Design

Street Design Skill

This skill provides comprehensive street design guidance based on NACTO Urban Street Design Guide, Global Designing Cities Initiative (GDCI), AASHTO Green Book, and international best practices. It covers the full workflow from street hierarchy classification through cross-section dimensioning, intersection design, streetscape specification, and traffic calming.

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1. Street Hierarchy Classification

Use the following decision tree to classify any street. Start with the Average Daily Traffic (ADT) count, then apply contextual modifiers.

Primary Classification by ADT and Function

Arterial (>15,000 ADT)

• Right-of-Way (ROW): 30-40m
• Lanes: 2-3 per direction (3.0-3.3m each)
• Design speed: 40-50 km/h (urban), 50-60 km/h (suburban)
• Transit: dedicated bus/BRT lanes strongly recommended
• Cycling: protected bike lanes required (physically separated)
• Pedestrian: wide sidewalks 3.6-6.0m, pedestrian refuge islands at crossings
• Median: 3.0-6.0m landscaped or transit median
• Signal spacing: 200-400m typical
• Role: city-wide movement, connects districts, carries transit trunk routes

Collector (3,000-15,000 ADT)

• ROW: 22-30m
• Lanes: 1-2 per direction (3.0-3.3m each)
• Design speed: 30-40 km/h
• Transit: on-street bus stops with boarding islands
• Cycling: protected bike lanes or buffered bike lanes
• Pedestrian: generous sidewalks 2.4-3.6m
• Median: optional, 1.8-3.0m where present
• Role: connects neighborhoods to arterials, local commercial corridors

Local Street (40%), reduce travel lane widths to minimum, add traffic calming, reduce noise through surface treatment | | Mixed-Use | Adaptive curbside management (flex zones for parking/loading/transit by time of day), wider pedestrian zones at ground-floor retail | | Industrial / Logistics | Wider travel lanes (3.3-3.6m) for trucks, larger corner radii, reinforced pavement, limit pedestrian/cyclist exposure to truck movements | | School Zone | 20-30 km/h speed limit, raised crossings at every intersection, flashing beacons, wide clear sidewalks, no on-street parking within 30m of entrance | | Hospital / Institutional | Accessible design priority, generous drop-off zones, clear wayfinding, audible pedestrian signals, level surfaces throughout | | Historic District | Narrower ROW acceptable, special materials and furnishings, heritage lighting, preservation of existing tree canopy and setbacks | | Waterfront / Park Edge** | Wider promenade (4.5-6.0m+), separated multi-use path, enhanced landscape buffer, view corridor preservation |

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2. Cross-Section Design Methodology

Design cross-sections layer by layer, working from the building face toward the street centerline. Each layer has a defined function and dimensional range.

Layer Sequence (Building Face to Centerline)

BUILDING FACE
  |
  |--> [A] Building Setback (context-dependent)
  |--> [B] Frontage Zone (0.3 - 0.9m)
  |--> [C] Pedestrian Clear Zone (1.8 - 3.6m)
  |--> [D] Furnishing / Planting Zone (0.6 - 1.8m)
  |--> [E] Cycle Track + Buffer (optional: 1.5-2.5m track + 0.3-0.6m buffer)
  |--> [F] Parking Lane (optional: 2.1 - 2.4m parallel, 4.5-5.5m angled)
  |--> [G] Travel Lane(s) (3.0 - 3.3m each)
  |--> [H] Median (optional: 1.2 - 6.0m)
  |
  CENTERLINE (mirror layers G through A for opposite side)

Layer Definitions

[A] Building Setback Not part of the public ROW but affects street enclosure. Zero setback for urban retail frontage, 1.5-3.0m for residential, 3.0-6.0m+ for suburban or institutional.

[B] Frontage Zone (0.3 - 0.9m) The strip immediately adjacent to the building face. Accommodates door swings, window displays, awning drip lines, basement vault covers. In commercial areas, may include outdoor dining or merchandise display (with permit, requiring wider dimension of 1.2-2.4m).

[C] Pedestrian Clear Zone (1.8 - 3.6m) The unobstructed walking path. This is the most critical pedestrian dimension. No street furniture, signs, trees, or other obstructions. Minimum 1.8m allows two wheelchairs to pass. Recommended 2.4m for residential, 3.0m for commercial, 3.6m+ for high-volume pedestrian areas. Must comply with ADA/accessibility requirements: maximum cross-slope 2%, smooth and continuous surface.

[D] Furnishing / Planting Zone (0.6 - 1.8m) Contains street trees, light poles, sign posts, parking meters, benches, trash receptacles, bicycle racks, utility access covers. Serves as a buffer between pedestrians and the roadway. Tree wells minimum 1.5m x 1.5m, continuous tree trench preferred. Bioswales and rain gardens can be integrated here.

[E] Cycle Track + Buffer (optional) One-way protected bike lane: 1.5m minimum, 2.0m recommended, 2.5m for high-volume. Two-way cycle track: 2.4m minimum, 3.0m recommended, 3.6m+ for high-volume. Buffer between cycle track and travel/parking lane: 0.3m minimum (painted), 0.6m recommended (with vertical elements such as bollards, planters, or curb).

[F] Parking Lane (optional) Parallel parking: 2.1m minimum, 2.4m recommended (allows door opening without encroaching on bike lane). Angled parking (45-degree): 4.5-5.5m. Angled parking (60-degree): 5.2-5.8m. Perpendicular parking (90-degree): 5.5-6.0m. Consider flex zones: parking by day, loading in morning, outdoor dining in evening.

[G] Travel Lane(s) General travel lane: 3.0m minimum urban, 3.3m standard (NACTO). Bus/transit lane: 3.3-3.6m. Right-turn lane: 2.7-3.0m. Left-turn lane: 3.0-3.3m. Never exceed 3.6m for any urban lane (wider lanes induce higher speeds). Reduce to 2.7m for yield streets and very low-speed environments.

[H] Median (optional) Pedestrian refuge: 1.8m minimum (2.4m with accessibility), allows stroller or wheelchair to wait. Landscaped median: 2.4-6.0m, with trees, ground cover, stormwater management. Transit median: 3.6-5.0m for center-running BRT/LRT with platforms. Left-turn pocket in median: 3.0-3.3m wide, 30-45m long.

Worked Example: Urban Collector Street (26m ROW)

   2.4m   |  3.0m  | 1.2m |2.0m|0.6| 2.4m | 3.0m | 3.0m | 3.0m | 2.4m |0.6|2.0m| 1.2m |  3.0m  | 2.4m
 Frontage  | Ped CZ | Furn |Bike|Buf| Park | Lane | Lane | Lane | Park |Buf|Bike| Furn | Ped CZ | Frontage
           |        | Zone |    |   |      |  EB  |  EB  |  WB  |      |   |    | Zone |        |
   BLDG ---+--------+------+----+---+------+------+------+------+------+---+----+------+--------+--- BLDG

Wait -- the above totals to more than 26m. Let me provide a corrected, realistic example:

Worked Example: Urban Collector (26m ROW, Commercial Context)

 0.6 | 3.0  | 1.2  | 2.0+0.6 | 2.4  | 3.0  | 3.0  | 2.4  | 0.6+2.0 | 1.2  | 3.0  | 0.6
Front|PedCZ | Furn | Bike+Buf | Park | Lane | Lane | Park | Buf+Bike | Furn | PedCZ|Front
     |      | Zone |          |      |  EB  |  WB  |      |          | Zone |      |
BLDG-+------+------+----------+------+------+------+------+----------+------+------+-BLDG
= 0.6+3.0+1.2+2.6+2.4+3.0+3.0+2.4+2.6+1.2+3.0+0.6 = 25.6m (~26m)

Worked Example: Residential Local Street (18m ROW)

 0.3 | 1.8  | 1.2  | 2.1  | 3.0  | 3.0  | 2.1  | 1.2  | 1.8  | 0.3
Front|PedCZ | Furn | Park | Lane | Lane | Park | Furn | PedCZ|Front
     |      | Zone |      |  NB  |  SB  |      | Zone |      |
BLDG-+------+------+------+------+------+------+------+------+-BLDG
= 0.3+1.8+1.2+2.1+3.0+3.0+2.1+1.2+1.8+0.3 = 17.8m (~18m)

Worked Example: Arterial Boulevard (36m ROW)

 0.6 | 3.6  | 1.5  | 2.0+0.6 | 3.3  | 3.3  | 3.3  | 4.8  | 3.3  | 3.3  | 0.6+2.0 | 1.5  | 3.6  | 0.6
Front|PedCZ | Furn | Bike+Buf | Lane | Lane | Lane | Med  | Lane | Lane | Buf+Bike | Furn | PedCZ|Front
     |      | Zone |          |  EB  |  EB  |  EB  |      |  WB  |  WB  |          | Zone |      |
BLDG-+------+------+----------+------+------+------+------+------+------+----------+------+------+-BLDG
= 0.6+3.6+1.5+2.6+3.3+3.3+3.3+4.8+3.3+3.3+2.6+1.5+3.6+0.6 = 37.9m (~38m, adjust median to 2.9m for 36m)

Worked Example: Shared Street / Woonerf (12m ROW)

 1.5   |          9.0 single shared surface           | 1.5
Planter|  pedestrians + cyclists + vehicles at 15km/h |Planter
 zone  |  textured paving, flush, no curbs, bollards  | zone
BLDG---+----------------------------------------------+---BLDG
= 1.5+9.0+1.5 = 12.0m

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3. Complete Street Elements Table

Pedestrian Zone Elements

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Sidewalk clear zone (residential) | 1.8m | 2.4m | 3.0m | Unobstructed walking path | | Sidewalk clear zone (commercial) | 2.4m | 3.0m | 4.5m | Higher pedestrian volumes | | Sidewalk clear zone (high-volume) | 3.0m | 3.6m | 6.0m+ | Transit stations, stadiums | | Frontage zone (retail) | 0.3m | 0.6m | 0.9m | Door swings, display | | Frontage zone (dining) | 1.2m | 1.8m | 2.4m | Outdoor seating permitted | | Furnishing zone | 0.6m | 1.2m | 1.8m | Trees, lights, furniture | | Curb ramp width | 1.2m | 1.5m | -- | ADA minimum | | Curb ramp slope | -- | 6.0% | 8.3% | ADA maximum |

Cycling Infrastructure

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Protected bike lane (1-way) | 1.5m | 2.0m | 2.5m | Physical separation required | | Protected bike lane (2-way) | 2.4m | 3.0m | 3.6m | Centerline marking required | | Conventional bike lane | 1.5m | 1.8m | 2.1m | Painted, no physical barrier | | Buffered bike lane | 1.5m + 0.6m | 1.8m + 0.9m | 2.1m + 1.2m | Lane + buffer width | | Shared bus-bike lane | 3.6m | 4.0m | 4.5m | Wide enough for passing | | Shared lane (sharrow) | 3.6m | 4.0m | -- | Full lane width, low speed only | | Separation buffer (painted) | 0.3m | 0.6m | 0.9m | Hatched markings | | Separation buffer (physical) | 0.6m | 0.9m | 1.5m | Bollards, planters, curbs | | Cycle track vertical separation | 50mm | 100-150mm | 200mm | Curb height above roadway |

Travel Lanes

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Travel lane (urban) | 2.7m | 3.0m | 3.3m | Never exceed 3.6m urban | | Travel lane (bus route) | 3.0m | 3.3m | 3.6m | Accommodates bus width | | Dedicated bus lane | 3.3m | 3.5m | 3.6m | Exclusive use | | BRT guideway | 3.5m | 3.6m | 4.0m | May need platforms | | Turn lane | 2.7m | 3.0m | 3.3m | Pocket length 30-45m | | Yield street (2-way, 1 lane) | 4.5m | 5.0m | 6.0m | Cars yield to pass |

Parking

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Parallel parking | 2.1m | 2.4m | 2.7m | Door zone consideration | | Angled parking (45-deg) | 4.5m | 5.0m | 5.5m | Stall depth | | Angled parking (60-deg) | 5.2m | 5.5m | 5.8m | Stall depth | | Perpendicular parking (90-deg) | 5.5m | 5.8m | 6.0m | Stall depth | | Parking stall length (parallel) | 5.5m | 6.0m | 6.6m | End-to-end | | Loading zone width | 2.4m | 3.0m | 3.6m | Wider for trucks | | Loading zone length | 9.0m | 12.0m | 18.0m | One to two vehicles |

Medians

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Pedestrian refuge island | 1.8m | 2.4m | 3.0m | Width perpendicular to crossing | | Landscaped median | 2.4m | 3.6m | 6.0m+ | Trees, planting, drainage | | Transit median (BRT/LRT) | 3.6m | 4.5m | 6.0m | Includes platform width | | Raised median (no planting) | 1.2m | 1.8m | 2.4m | Concrete or paved |

Street Furniture and Fixtures

| Element | Minimum | Recommended | Maximum | Notes | |---------|---------|-------------|---------|-------| | Tree well (individual) | 1.2x1.2m | 1.5x1.5m | 2.0x2.0m | Open or grated | | Tree trench (continuous) | 0.9m wide | 1.2m wide | 1.8m wide | Shared soil volume | | Street tree spacing | 6.0m | 7.5-9.0m | 12.0m | Center to center | | Lighting pole (pedestrian) | -- | 4.0-6.0m ht | 6.0m ht | Warm white 3000K | | Lighting pole (roadway) | 8.0m ht | 10.0-12.0m ht | 15.0m ht | Mount above canopy | | Bench | 0.6m depth | 0.45x1.8m | -- | With armrests and back | | Bollard spacing | 1.2m | 1.5m | 1.8m | Allow wheelchair passage | | Bicycle rack | 0.6x1.8m | 0.6x2.0m | -- | Per inverted-U rack | | Trash receptacle | -- | 0.6x0.6m | -- | One per block face | | Transit shelter | 1.5x3.0m | 1.5x4.5m | 1.5x6.0m | Clear of pedestrian path |

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4. Intersection Design

Compact Intersection Principles

Design intersections to be as compact as possible. Smaller intersections reduce pedestrian crossing distances, slow turning vehicles, improve sight lines, and reduce conflict points. Key principles:

• Minimize curb radii (tightest feasible for design vehicle)
• Eliminate unnecessary turn lanes
• Use curb extensions (bulb-outs) to shorten crossings
• Align crosswalks with pedestrian desire lines
• Provide pedestrian refuge islands for crossings >3 lanes
• Set back stop bars 1.2-2.4m from crosswalk (4.0m at signalized with bike box)

Curb Radius Standards

| Context | Effective Radius | Notes | |---------|-----------------|-------| | Tight urban (no buses) | 1.5-3.0m | Car-only turns, slow speed | | Standard urban | 3.0-4.5m | Accommodates SUVs and vans | | Urban with buses | 7.5-10.5m | Or use mountable truck apron | | Suburban | 6.0-9.0m | Higher speed turns | | With frequent trucks | 9.0-12.0m | Design vehicle WB-50 or WB-67 |

Note: Effective turning radius is often larger than the physical curb radius due to parking lane and bike lane setbacks. A 3.0m physical curb radius with a 2.4m parking lane yields an effective radius of approximately 7.5m, sufficient for buses and delivery trucks.

Pedestrian Crossing Types

| Type | Application | Key Dimensions | |------|-------------|----------------| | Marked crosswalk (standard) | All intersections, low-speed streets | 1.8m minimum width, 3.0m standard | | High-visibility continental | Arterials, collectors, school zones | 3.0m minimum, white bars 0.3-0.6m wide, 0.3-0.6m gaps | | Raised crossing | Speed reduction desired, school zones, pedestrian priority areas | Full crosswalk width, 75-100mm raise, 1:10 to 1:25 approach ramps | | Signalized crossing | Arterials, >6,000 ADT, >3 lanes | Pedestrian signal head, push button or automatic detection | | HAWK / PHB | Mid-block crossings, high-speed roads | Overhead beacon, pedestrian-activated, dark until activated | | Pedestrian scramble | High pedestrian volumes, complex intersections | All-walk phase, diagonal crossing permitted |

Crossing Width Standards

| Context | Minimum | Standard | High-Volume | |---------|---------|----------|-------------| | Residential | 1.8m | 2.4m | 3.0m | | Commercial | 3.0m | 3.6m | 4.5m | | Transit station / arena | 3.6m | 4.5m | 6.0m+ |

Signal Timing for Pedestrians

• Minimum pedestrian walk phase: 7 seconds
• Pedestrian walking speed for clearance calculation: 1.2 m/s (standard), 1.0 m/s (elderly/school zones), 0.9 m/s (accessible design)
• Leading Pedestrian Interval (LPI): 3-7 seconds head start before parallel vehicle green
• Exclusive pedestrian phase (scramble): 15-25 seconds depending on crossing distances
• Pedestrian recall: recommended at all urban intersections (automatic pedestrian phase every cycle)
• Maximum wait time: 60-90 seconds (longer waits lead to non-compliance)

Roundabout Design

| Type | Inscribed Diameter | Capacity (veh/day) | Speed | Application | |------|-------------------|---------------------|-------|-------------| | Mini | 13-25m | <15,000 | 15-25 km/h | Low-volume local streets, traffic calming | | Single-lane | 25-30m | 15,000-25,000 | 25-35 km/h | Collectors, neighborhood gateways | | Multi-lane | 45-55m | 25,000-45,000 | 30-40 km/h | Arterials, suburban intersections |

Roundabout pedestrian crossings: set back one car length (6.0m) from yield line, marked crosswalk, splitter island refuge minimum 1.8m wide.

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5. Streetscape and Materials

Surface Materials by Zone

| Zone | Primary Materi

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Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: Amanbh997
• Source: Amanbh997/Urban-Design-Skills-Claude
• License: MIT

Install and usage instructions live in the source repository linked above.