Draft Concept Alternatives Analysis
Comparing the 3 design alternatives under evaluation by the City of Mountain View for the 1.7-mile Rengstorff corridor.
| Dimension | Concept 1: Buffered Baseline | Concept 2: Class IV Road Diet | Concept 3: AAA Green Spine |
|---|---|---|---|
| Bikeway Class | Class IIB (Painted 2–3 ft Buffer) | Class IV Separated (Curb / Delineator) | Class IV 2-Way Sidepath / Cycle Track |
| Lane Geometry | Maintains 4 lanes (where existing) | 4-to-3 Road Diet (1 lane/dir + TWLTL) | 2 Lanes + Consolidated Turn Bays |
| Crash Reduction (CMF) | 10–15% (CMF: 0.85–0.90) | 35–47% (CMF: 0.53–0.65) | 48–55% (CMF: 0.45–0.52) |
| Traffic Stress (LTS) | LTS 3–4 (High Stress) | LTS 2 (Low Stress) | LTS 1 (All-Ages 8-80) |
| On-Street Parking | 95–100% Preserved | 50–65% Preserved (1 Side / Pockets) | 5–25% Preserved (Substantial Loss) |
| Transit Stops (VTA 40) | Curbside in-lane (bus-bike weave) | Floating Bus Islands (Bikes behind) | Floating Islands + Signal Priority |
| Green Infrastructure | Minimal (existing footprints) | Moderate (swales at curb extensions) | Maximum (continuous 6 ft bioswales) |
| Cost Estimate | $1.2M – $2.5M (Quick-build) | $4.5M – $8.0M (Medium civil) | $14.0M – $22.0M+ (Heavy civil) |
Focuses on low-cost paint and signage within existing curb lines. Upgrades standard bike lanes with 2–3 ft painted buffers and green conflict paint.
- Preserves ~95%+ on-street parking across the corridor.
- Retains 4-lane vehicle capacity in northern segments.
- Leaves cyclists exposed to door-zone hazards and vehicle incursions.
- Fails to meet Mountain View Vision Zero 2030 safety targets.
Converts 4-lane segments to 1 travel lane in each direction + a continuous Two-Way Left-Turn Lane (TWLTL) and directional Class IV protected bike lanes.
- Delivers 35–47% crash reduction (proven FHWA road diet model).
- Floating bus boarding islands eliminate VTA bus-bike weaving conflicts.
- Continuous center turn lane functions as emergency vehicle bypass.
- Preserves parking on one side in high-density multifamily zones.
Reclaims maximum right-of-way for active transportation, featuring a 10–12 ft two-way protected sidepath/promenade and continuous stormwater bioswales.
- Highest safety score (LTS 1 / 8-to-80 all-ages comfort).
- Adds 120+ mature shade trees and linear bioretention cells.
- Removes 75–95% of on-street parking (severe multifamily impact).
- Highest capital cost ($14M–$22M+) and longest construction disruption.
Engineered Intersection Safety Treatments
Key countermeasures integrated into the preferred Complete Streets designs to protect vulnerable road users.
1. Dutch-Style Protected Intersections
Implemented at major junctions (Middlefield Rd, California St, and Central Expy). Features corner setback islands that force turning vehicles to slow down to 10–15 mph and place cyclists directly in the driver’s primary forward viewing cone before turn execution.
• Includes forward bicycle queue boxes for smooth left-turn positioning.
2. Leading Pedestrian & Bike Intervals (LPI/LBI)
Programmed 3- to 7-second head start for pedestrians and cyclists before adjacent vehicular green lights are activated.
• Reduces pedestrian-vehicle conflict incidents by up to 60% (FHWA).
3. Assembly Bill 413 Daylighting & Red Curbs
Mandates a minimum 20-foot parking-free clear zone upstream of all marked crosswalks and intersections.
• Enforced through physical curb bulb-outs and bioswale extensions.
4. Floating Transit Boarding Islands
Replaces curbside pull-in bus stops with dedicated concrete boarding platforms for VTA Route 40.
• Eliminates transit delay (buses do not lose time merging back into traffic).