Inputs & assumptions
The green roof is built from standardized modules per Future Green’s Schematic Design for the NYC pilot. A shelter takes the maximum modules that fit its model (no partial coverage); the selected coverage option sets each module’s size, the soil profile, and the planting. Cooling and cost values are provisional, to be updated as the Brownsville pilot is monitored.
| Coverage options | Full coverage: 3′9″×3′8.5″ modules (≈13.9 SF each), 1.75″ media + ½″ drain mat, pre-grown sedum mat + native annual seed. Half coverage: 1′10.5″×3′8.5″ modules (≈7.0 SF each), 5.5″ media + ½″ drain mat, native perennial plugs + native annual seed. Both use 3 modules on the 14′ model (≈42 SF full / ≈21 SF half). |
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| Modules per model | From the DOT inventory + NYC JCDecaux dims: 14′ (4-section) → 3, 10′ (2-section short) → 2. Solar models take one fewer (the roof PV panel occupies ~one module’s footprint). Narrow shelters (3′6″ deep) are out of scope — the 3′8.5″ module is too deep to fit. (Solar coverage + the narrow case are best estimates pending Future Green confirmation.) |
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| Soil & storage | Stored-water depth = media×0.30 + drain×0.25 (CNT Green Values storage method; porosities assumed, to confirm against Future Green’s media + drain-mat products). Full → 0.65″ storage; Half → 1.78″. CNT Green Values. |
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| Retention (per storm) | area × min(storm, storage) × 0.62 gal/in/ft². On a 14′ shelter at a 1″ storm: Full ≈ 17 gal (more area, shallow — storage-limited at 0.65″), Half ≈ 13 gal (less area, deep — rain-limited). For storms > ~1.3″ the deeper Half option retains more. Both are well below the earlier generic 70 ft² placeholder — an honest downward revision to the prototype’s real size. |
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| Retention (annual) | area × the NOAA daily-rainfall capture depth at the option’s storage (NOAA GHCN-Daily, Central Park 1991–2020; daily green-roof water balance with FAO-56 Hargreaves ET, calibrated to the ~50% reported for temperate extensive roofs — Mentens et al. 2006). Full’s larger area generally yields more annual gallons; Half’s deeper media captures a higher fraction. |
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| Cooling effect PROVISIONAL | Under-shelter heat-stress reduction, in two cited parts: sheltering ≈4°F (a stainless-steel frame with glass roof — the NYC type — gave the largest heat-stress reduction of four designs, Yang et al. 2024); the green roof adds up to ≈2°F on a 70 ft² reference roof (Wang et al. 2025), scaling with the module area. The two options differ mainly via area; the sedum-vs-perennial transpiration difference is real but within this provisional band. Pending Columbia pilot. |
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| Planting & pollinators | Full coverage uses a sedum mat (lower native-pollinator value); Half coverage uses native perennial plugs (higher value). This is shown as a qualitative flag on the Biodiversity lens; it does not change the connectivity score, which is a position-based siting heuristic that doesn’t read the roof’s own plants. |
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| Retrofit cost ROM | $1,400 – $7,000 per shelter (rough order of magnitude). Dominated by fixed structural/labour cost rather than roof area. To be refined with the team. |
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Green-roof specs are from Future Green’s Schematic Design for the NYC Green Roof Bus Shelter Pilot (PDF link to follow).
Agency lineage
Where possible, lenses align with frameworks already in use at NYC agencies, to avoid duplicate measurement burden and to slot into existing decision-making processes (NPCC standardization work, OMB capital-project intake).
| Heat | NYC CEJ heat metrics (Helen Cooper). Community framing reports the share of in-scope stops in high-HVI areas (NYC DOHMH Heat Vulnerability Index ≥ 4), alongside the pedestrian demand of the served streets (NYC DOT Pedestrian Mobility Plan — nearest-segment category, most-common across a scope). Replaces the earlier route-summed ridership proxy, which was not a reliable stop-level signal. |
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| Stormwater | Per-storm retention from the CNT Green Values Calculator green-roof storage method (substrate + drainage water-holding volume); annual retention from NYC’s measured rainfall (NOAA Central Park) via a daily green-roof water balance with evapotranspiration. Community framing reports the share of in-scope stops in high flood-burden areas (NYC MOCEJ FSHRI ≥ 4). Aligns with NYC MOUA conservation metrics (NY State Soil & Water District) + NYC DEP Green Acres standards. |
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| Biodiversity LOW CONF. | Pollinator habitat connectivity, as a gap-crossing stepping-stone score per shelter (landscape-connectivity method — Saura & Pascual-Hortal 2007; anchored to solitary-bee foraging ~250–300 m — Gathmann & Tscharntke 2002). A siting heuristic, not a measured benefit: green-roof-as-habitat evidence is weak and a shelter roof may be below the effective stepping-stone threshold. Patches = NYC parks (DPR) + MOUA urban-agriculture sites + DEP green infrastructure (plant-bearing only — concrete-top infiltration basins excluded) + 2015 street-tree census (alive). GI points and street trees that fall inside a park are dropped (the park already represents that habitat). Each patch is weighted by habitat capacity — weight = √(habitat area): park area from geometry, GI from asset_area, gardens a nominal 500 m², each street tree ~12 m² — following the Probability-of-Connectivity convention (area-weighted patch attributes) so a bridge value = wA·wB·p(dA)·p(dB): a large park outranks a single small GI point (the √ keeps it sub-linear, so a cluster of small GI no longer wins by sheer count). On the map the lens shows the green spaces within ~300 m of a stop; in Single-shelter scope, arcs link the selected stop to its nearest reachable patches and street trees. |
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| Air quality | Foregone in this evaluation phase — shelter-scale sensors are physically too large and approval timelines do not fit the current pilot window. |
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What each lens reports
- Heat — the under-shelter heat-stress reduction (sheltering + green roof), the share of in-scope stops in high-HVI areas, and pedestrian demand.
- Stormwater — per-shelter retention per 1″ storm, total retention across the scenario, and the share of in-scope stops in high flood-burden areas.
- Biodiversity — the connectivity score, how many shelters act as stepping stones, and what each bridges (tree, park, garden, GI).
Per-shelter figures (cooling, retention) are non-additive across shelters, so multi-shelter scopes report a representative value; totals are shown only where they genuinely sum (retention gallons).
Scope
- All sheltered stops are eligible. The scenario operates on every existing bus-shelter stop (≤25 m shelter–stop match); the viable-typology gate has been removed. Stops with no shelter are shown for context (binary sheltered/unsheltered) but excluded from the scenario.
- Structural capacity — which JCDecaux typologies can carry a green-roof load is still to be confirmed with the team; for now all sheltered stops are modifiable.
- Single-shelter scope defaults to the Brownsville pilot stop (Pitkin Av & Saratoga Av); click any shelter on the map to switch.
- Borough scope aggregates shelters by borough. Finer-grained NTA / Climate Strong Communities geographies are future work.
Open work
- Biodiversity lens — pending Columbia measurement capacity + partner institution coordination.
- NTA & Climate Strong Communities geographies for a finer-than-borough scope.
- Formal DEP "green acres" translation for stormwater community-scale row.
- OMB capital-project key indicators + Technical Appendix B alignment.
- Helen (CEJ) & Kiana (MOUA) metric-table integration once permission to share is confirmed.
- Designed PDF tear sheet (currently uses browser print stylesheet).
Data sources
- Bus routes / stops: MTA
- Bus shelters (model, canopy, solar): NYC DOT (JCDecaux inventory)
- Pedestrian demand: NYC DOT Pedestrian Mobility Plan — Pedestrian Demand (nearest-segment category)
- Heat Vulnerability Index (HVI): NYC DOHMH 2024 (by MODZCTA)
- Flood Vulnerability (FSHRI): NYC MOCEJ 2024 (by census tract)
- Biodiversity patches: NYC DPR parks; NYC MOUA urban-agriculture sites; NYC DEP green infrastructure; NYC 2015 Street Tree Census
- Green-roof stormwater retention: CNT Green Values Calculator methodology (per-storm storage volume)
- Rainfall (annual retention model): NOAA NCEI GHCN-Daily, NY City Central Park (USW00094728), 1991–2020 normals
- Cooling: Yang et al. 2024 (bus-shelter thermal study); green-roof pedestrian cooling (Wang et al. 2025) — provisional