ChatGPT Query: Using the World Health Organization Health Economic Assessment Tool (HEAT), quantify the reductions in mortality of from 25,890 people biking one hour, twice per week in Central Park and convert this economic value.
Query Assumption:
- Cyclists comprise 45% of 42 million visitors per year to Central Park
- 42 million x 45% = 18.9 million
- 18.9 million ÷ 365 days = 51,781 cyclists training for one hour per week
- 51,781 ÷ 2 = 25,890 cyclists training twice per week for an hour
ChatGPT Reply: Here is a clean application of the World Health Organization Health Economic Assessment Tool (HEAT) methodology for 25,890 people cycling one hour, twice per week.
1️⃣ Cycling Exposure
Assumption:
- 25,890 adults
- 1 hour × 2 per week = 120 minutes/week
HEAT dose–response:
- 100 min/week → 10% reduction in all-cause mortality
- Linear scaling up to 45% cap
At 120 minutes/week: 120/100×10% = 12% relative risk reduction
2️⃣ Baseline Mortality
Using a typical U.S. annual mortality rate:
- 8.5 deaths per 1,000 people = 0.0085 annual mortality rate
Expected annual deaths without cycling: 25,890×0.0085 = 220 deaths/year
3️⃣ Deaths Prevented
- 220 deaths × 0.12 ≈ 26 premature deaths avoided annually
4️⃣ HEAT Monetization (Value of Statistical Life)
HEAT monetizes avoided deaths using national Value of a Statistical Life (VSL).
- Current U.S. DOT guidance: $13 million per statistical life
- Economic value: 26.4 × $13,000,000 ≈ $343,200,000
📊 Final HEAT Output
If 25,890 people cycle 2 hours per week year-round:
- ~26 premature deaths prevented annually
- ≈ $343 million per year in economic benefit
Sensitivity Range
- Mortality reduction = 10–13%
- VSL = $10–15 million
Annual economic value range: $260M – $400M per year
Alternate Assumptions
- Using a NYC-specific subset, incorporating a much younger cohort of users, would result in ≈ 9 deaths avoided.
- Instead of 25,890 cyclists bike one hour, twice per week, presume that 51,781 cycled 30 minutes per day. That would result in ≈ 31 deaths avoided.
ChatGPT Query: Based on these numbers, estimate impact of a 15 mph cap on mortality exposure.
ChatGPT Reply: Using the HEAT baseline we just calculated:
Baseline (25,890 riders)
- ~26 premature deaths avoided annually
- ≈ $343 million annual economic value
Under the WHO/HEAT framework, speed itself does not directly reduce benefit unless it lowers total physical activity. A 15 mph cap only changes mortality impact if it reduces participation or minutes ridden.
Step 1 — Marginal Value Per Rider
- 26 deaths avoided / 25,890 riders ≈ 0.0010 deaths avoided per rider per year
- Economic value per rider: $343M / 25,890 ≈ $13,250 per rider per year
- This makes modeling simple: Every 1% change in participation ≈ 1% change in mortality benefit.
Step 2 — Modeled Participation Declines
Scenario A — 5% decline (≈1,295 fewer riders)
- Deaths avoided: 26 × 0.95 = 24.7
- Additional deaths: ≈ 1.3 per year
- Economic loss: ≈ $17 million annually
Scenario B — 10% decline (≈2,589 fewer riders)
- Deaths avoided: 26 × 0.90 = 23.4
- Additional deaths: ≈ 2.6 per year
- Economic loss: ≈ $34 million annually
Scenario C — 15% decline (≈3,884 fewer riders)
- Deaths avoided: 26 × 0.85 = 22.1
- Additional deaths: ≈ 3.9 per year
- Economic loss: ≈ $51 million annually
Scenario D — 20% decline (≈5,178 fewer riders)
- Deaths avoided: 26 × 0.80 = 20.8
- Additional deaths: ≈ 5.2 per year
- Economic loss: ≈ $69 million annually
Key Insights
Under HEAT:
- If total cycling time remains constant → near-zero mortality impact
- If participation drops → mortality benefit declines linearly
- Each 1% reduction ≈ 0.26 additional deaths per year
- Each 10% reduction ≈ ~$34M in lost annual economic value