{
  "updated": "2026-08-25",
  "note": "Published estimates of automobile external costs — costs imposed on other people, not the driver’s gas and car payment. Packs are not averaged together. Inflation uses CPI-U to 2024 dollars. Null means the study did not publish that line.",
  "cpi2024": 313.689,
  "cpi": {
    "2002": 179.9,
    "2005": 195.3,
    "2016": 240.007,
    "2017": 245.12,
    "2019": 255.657,
    "2020": 258.811,
    "2023": 304.702,
    "2024": 313.689
  },
  "defaults": {
    "milesPerYear": 11106,
    "milesSource": "FHWA Highway Statistics 2023 Table VM-1. Light-duty miles per registered vehicle.",
    "mpg": 22.6,
    "mpgSource": "FHWA Highway Statistics 2023 Table VM-1. Light-duty average (cars, vans, pickups, SUVs).",
    "kwhPer100Miles": 39,
    "kwhSource": "EPA Green Vehicle Guide: model-year 2025 median EV, 39 kWh/100 miles combined."
  },
  "us": {
    "year": 2023,
    "lightDutyVmt": 2879076000000,
    "lightDutyVehicles": 259238294,
    "milesPerVehicle": 11106,
    "mpg": 22.6,
    "occupancy": 1.52,
    "allVmt": 3246817000000,
    "source": "FHWA Highway Statistics 2023 Table VM-1. Light-duty is cars, vans, pickups, and SUVs. Occupancy is light-duty person-miles / vehicle-miles."
  },
  "climate": {
    "kgCo2PerGallon": 8.887,
    "kgNote": "EPA greenhouse-gas equivalencies: 8.887 × 10⁻³ metric tons CO2 per gallon of gasoline.",
    "kgSource": "https://www.epa.gov/energy/greenhouse-gases-equivalencies-calculator-calculations-and-references",
    "parryBaselineMpg": 20,
    "parryBaselineNote": "Parry Table 2: greenhouse 6¢/gal and 0.3¢/mi, oil 12¢/gal and 0.6¢/mi, so the published per-mile lines assume 20 mpg. This page rescales those fuel lines with the mpg slider.",
    "scc": [
      {
        "id": "epa2025",
        "label": "EPA 2023 SC-CO2, 2% near-term Ramsey, 2025 emissions",
        "usdPerTon": 210,
        "dollarYear": 2020,
        "source": "EPA Report on the Social Cost of Greenhouse Gases (Dec 2023), Table ES.1"
      },
      {
        "id": "iwg2020",
        "label": "IWG 2021 interim SC-CO2, 3% (often used 2010s–2021)",
        "usdPerTon": 51,
        "dollarYear": 2020,
        "source": "Interagency Working Group SC-GHG TSD, February 2021"
      }
    ]
  },
  "electric": {
    "kwhPer100Miles": 39,
    "kwhNote": "EPA Green Vehicle Guide comparison tool: typical new EV is the MY2025 median, 39 kWh/100 miles combined city/highway.",
    "kwhSource": "https://www.epa.gov/greenvehicles/comparison-your-car-vs-electric-vehicle",
    "lbCo2PerMwh": 767.2,
    "gridYear": 2023,
    "gridNote": "EPA eGRID 2023 US average output emission rate: 767.2 lb CO2/MWh. This is generation-weighted, not a specific utility.",
    "gridSource": "https://www.epa.gov/egrid/summary-data",
    "note": "Electric: oil dependence and tailpipe air go to zero. Congestion, crashes, and parking do not. Climate is kWh × US-average grid CO2 × EPA 2023 SCC. Non-exhaust PM (tires, brakes, road dust) is not in Parry’s local-air line and is not added here."
  },
  "congestionScale": {
    "note": "Parry’s 5¢/mi congestion line is a US average across rural, urban, peak, and off-peak. Peak travel in large metros is several times that. Do not scale the whole pack by the peak ratio — only congestion moves that much.",
    "source": "Ian W.H. Parry, “Pricing Urban Congestion,” RFF Discussion Paper 08-35, 2008.",
    "url": "https://www.rff.org/publications/working-papers/pricing-urban-congestion/",
    "national": { "centsPerMile": 5.0, "dollarYear": 2005, "label": "Parry / FHWA nationwide average" },
    "peak": [
      { "id": "dc", "label": "Washington, DC peak, 2002", "centsPerMile": 28.0, "dollarYear": 2002 },
      { "id": "chicago", "label": "Chicago peak (scaled from DC delay)", "centsPerMile": 33.7, "dollarYear": 2002 },
      { "id": "detroit", "label": "Detroit peak (scaled from DC delay)", "centsPerMile": 23.5, "dollarYear": 2002 }
    ],
    "rangeNote": "Mohring (1999), cited there: Twin Cities peak from under 2.5¢ to over 50¢/mi across road classes (then-year dollars)."
  },
  "gasTax": {
    "federalCentsPerGallon": 18.4,
    "note": "Federal gasoline tax has been 18.4¢/gal since 1993. State taxes vary. This page only subtracts the federal rate, as a lower bound on what drivers already pay per mile toward roads.",
    "source": "IRS / FHWA. Rate unchanged in nominal dollars since 1993."
  },
  "parking": {
    "label": "Parking (bundled subsidy)",
    "centsPerMile": 20.0,
    "dollarYear": 2023,
    "source": "Todd Litman, “Transportation Cost Estimates,” Victoria Transport Policy Institute, Table 3, gasoline car, $0.20/mi.",
    "url": "https://www.vtpi.org/tce.pdf",
    "note": "Bundled into rents, wages, and prices rather than paid per trip (Shoup). A subsidy, not soot from the extra mile. Parry omits it. Included on US packs; the checkbox turns it off."
  },
  "packs": [
    {
      "id": "parry",
      "title": "Parry, Walls & Harrington 2007",
      "short": "Parry 2007",
      "kind": "published-bundle",
      "dollarYear": 2005,
      "unit": "usdPerVehicleMile",
      "appendParking": true,
      "place": "United States, national average",
      "what": "JEL 2007 marginal cost of an extra mile: congestion, external crashes, local air, 2005 climate, oil. Parking is Litman’s line, off in the original table. Fuel lines scale with mpg (his 20 mpg). Electric zeros oil and tailpipe air; climate becomes US-average grid × EPA 2023 SCC.",
      "source": "Ian W.H. Parry, Margaret Walls, and Winston Harrington, “Automobile Externalities and Policies,” Journal of Economic Literature 45(2), 2007, Table 2.",
      "url": "https://www.aeaweb.org/articles?id=10.1257/jel.45.2.373",
      "items": [
        { "id": "congestion", "label": "Congestion", "centsPerMile": 5.0 },
        { "id": "crashes", "label": "Crashes (external)", "centsPerMile": 3.0 },
        { "id": "localAir", "label": "Local air pollution", "centsPerMile": 2.0, "fuel": "tailpipe" },
        { "id": "climate", "label": "Greenhouse gases", "centsPerMile": 0.3, "fuel": "gasoline", "baselineMpg": 20 },
        { "id": "oil", "label": "Oil dependence", "centsPerMile": 0.6, "fuel": "gasoline", "baselineMpg": 20 }
      ]
    },
    {
      "id": "parryEpa",
      "title": "Parry categories, EPA 2023 climate",
      "short": "Parry, new climate",
      "kind": "hybrid",
      "dollarYear": 2005,
      "unit": "usdPerVehicleMile",
      "appendParking": true,
      "place": "United States",
      "what": "Parry’s non-climate lines, CPI-inflated, plus Litman parking. Climate is gallons or grid kWh × EPA 2023 SCC ($210/ton in 2020$). MPG and kWh/mi move climate. Congestion, crashes, and parking do not.",
      "source": "Parry et al. 2007 Table 2 (non-climate lines) + EPA SC-GHG 2023 Table ES.1 + FHWA VM-1 2023 mpg + EPA gasoline CO2 factor.",
      "url": "https://www.epa.gov/environmental-economics/scghg",
      "replaceClimate": "epa2025",
      "items": [
        { "id": "congestion", "label": "Congestion", "centsPerMile": 5.0 },
        { "id": "crashes", "label": "Crashes (external)", "centsPerMile": 3.0 },
        { "id": "localAir", "label": "Local air pollution", "centsPerMile": 2.0, "fuel": "tailpipe" },
        { "id": "climate", "label": "Greenhouse gases (EPA 2023 SCC)", "centsPerMile": null, "fuel": "energy" },
        { "id": "oil", "label": "Oil dependence", "centsPerMile": 0.6, "fuel": "gasoline", "baselineMpg": 20 }
      ]
    },
    {
      "id": "litman",
      "title": "Litman / VTPI cost estimates",
      "short": "Litman / VTPI",
      "kind": "published-bundle",
      "dollarYear": 2023,
      "unit": "usdPerVehicleMile",
      "place": "Typical North American conditions (compilation)",
      "what": "Litman’s gasoline-car table: unpaid roadway, parking, barrier, noise/air. Fuel taxes cover about half of his roadway line; the unpaid half stays. Resource/fuel scales with mpg and drops for an EV.",
      "source": "Todd Litman, “Transportation Cost Estimates,” Victoria Transport Policy Institute, Table 3 (gasoline car). Roadway unpaid = half of $0.080/mi, following his own split that fuel taxes cover about half of roadway costs.",
      "url": "https://www.vtpi.org/tce.pdf",
      "items": [
        { "id": "congestion", "label": "Congestion", "centsPerMile": 4.0 },
        { "id": "crashes", "label": "Crashes (external)", "centsPerMile": 5.0 },
        { "id": "noiseAir", "label": "Noise and air pollution", "centsPerMile": 5.0 },
        { "id": "barrier", "label": "Barrier effect", "centsPerMile": 2.0 },
        { "id": "resource", "label": "Resource / fuel externalities", "centsPerMile": 2.0, "fuel": "gasoline", "baselineMpg": 22.6 },
        { "id": "roadway", "label": "Unpaid roadway (½ of his roadway line)", "centsPerMile": 4.0 },
        { "id": "parking", "label": "Parking (bundled subsidy)", "centsPerMile": 20.0 }
      ]
    },
    {
      "id": "delft",
      "title": "CE Delft Handbook 2019",
      "short": "CE Delft EU",
      "kind": "eu-average",
      "dollarYear": 2016,
      "unit": "eurCentsPerPkm",
      "place": "EU-28 average, 2016",
      "what": "EU-28 average, 12.0 €-cent per passenger-km with congestion, converted with US occupancy and the 2016 euro. Average, not marginal; gasoline-era Europe; gas/electric controls do not rewrite it.",
      "source": "CE Delft, “Handbook on the external costs of transport,” Version 2019, Figure 15 / text: 7.8 €-cent/pkm without congestion, 12.0 €-cent/pkm with congestion. EUR/USD 2016 annual average 1.107 (IRS).",
      "url": "https://cedelft.eu/publications/handbook-on-the-external-costs-of-transport-version-2019/",
      "eurUsd": 1.107,
      "euroCentsPerPkm": 12.0,
      "euroCentsPerPkmNoCongestion": 7.8,
      "items": [
        { "id": "bundle", "label": "EU handbook average (with congestion)", "euroCentsPerPkm": 12.0 }
      ]
    }
  ],
  "glossary": [
    {
      "id": "congestion",
      "label": "Congestion",
      "packs": ["parry", "parryEpa", "litman", "delft"],
      "kind": "Per extra vehicle-mile",
      "body": "Delay you impose on everyone else already on the road. Your own time is private. Parry’s 5¢/mi (2005$) is a US average. His later work puts Washington, DC peak around 28¢/mi in 2002$ — several times the nationwide line after inflation. An EV still takes a slot."
    },
    {
      "id": "crashes",
      "label": "Crashes (external)",
      "packs": ["parry", "parryEpa", "litman", "delft"],
      "kind": "Per extra vehicle-mile",
      "body": "Harm this extra mile imposes on other people, net of what occupants already bear. Your own injury risk is mostly private. NHTSA’s huge ‘social cost’ includes occupant harm; Parry’s line is the slice on strangers. No separate EV crash number here."
    },
    {
      "id": "localAir",
      "label": "Local air pollution",
      "packs": ["parry", "parryEpa"],
      "kind": "Mostly tailpipe, per mile",
      "body": "Nearby NOx, VOCs, and PM. Parry treated it as per-mile because US standards are per mile. Electric sets this to zero (no tailpipe). Tire, brake, and road dust are not in his 2007 figure and are not added."
    },
    {
      "id": "noiseAir",
      "label": "Noise and air pollution",
      "packs": ["litman"],
      "kind": "Litman combined line",
      "body": "Litman bundles traffic noise with local air. EVs are quieter at low speed; tire noise remains. His line is not split when you toggle electric."
    },
    {
      "id": "climate",
      "label": "Greenhouse gases",
      "packs": ["parry", "parryEpa"],
      "kind": "Per gallon or per kWh",
      "body": "CO2 damage. Parry 2007: about 0.3¢/mile at 20 mpg. Parry, new climate prices the same gallons or grid kWh at EPA’s 2023 SCC ($210/ton in 2020$). Gasoline: 8.887 kg CO2/gallon. Electric: eGRID US average. This is what the mpg / kWh slider moves."
    },
    {
      "id": "oil",
      "label": "Oil dependence",
      "packs": ["parry", "parryEpa"],
      "kind": "Per gallon",
      "body": "Security and disruption costs of burning oil — not the pump price. Scales with gallons. Zero on electric."
    },
    {
      "id": "resource",
      "label": "Resource / fuel externalities",
      "packs": ["litman"],
      "kind": "Per gallon, Litman compilation",
      "body": "Litman’s catch-all for fuel externalities beyond the pump. Scales with mpg; drops for an EV. Not the same split as Parry’s oil + climate."
    },
    {
      "id": "parking",
      "label": "Parking (bundled subsidy)",
      "packs": ["parry", "parryEpa", "litman"],
      "kind": "Land subsidy, not tailpipe damage",
      "body": "Cost of storing the car that is not paid per trip — bundled into rents, wages, and prices (Shoup). Litman: $0.20/mi. Parry omitted it. Included on US packs; uncheck to drop it. An EV still needs a space."
    },
    {
      "id": "roadway",
      "label": "Unpaid roadway",
      "packs": ["litman"],
      "kind": "Infrastructure not covered by fuel tax",
      "body": "Roads cost more than fuel taxes bring in. Litman’s roadway line is 8¢/mi; he says taxes cover about half, so 4¢ stays unpaid. Federal gas tax is 18.4¢/gal — about 0.8¢/mi at the US light-duty average."
    },
    {
      "id": "barrier",
      "label": "Barrier effect",
      "packs": ["litman"],
      "kind": "Per extra vehicle-mile",
      "body": "Delay and danger for people walking or biking across a stream of cars. Not congestion among drivers. Litman includes it; Parry does not."
    },
    {
      "id": "bundle",
      "label": "EU handbook average",
      "packs": ["delft"],
      "kind": "Average € per passenger-km, not a US extra mile",
      "body": "CE Delft 2019: accidents, air, climate, noise, congestion, well-to-tank, and habitat for EU-28 cars — 12.0 €-cent/pkm with congestion. Converted with occupancy and the 2016 euro. Average, not Parry’s extra mile. Gas/electric does not rewrite it."
    },
    {
      "id": "notCounted",
      "label": "Not in these packs",
      "packs": [],
      "kind": "Private costs, mostly",
      "body": "Gasoline, electricity, depreciation, your time, and crash risk you bear yourself. Large, and mostly private. Inactivity, longevity, shop sales, and living in a car place versus a transit place are a different object — <a href=\"place.html\">Place, time, health</a>. Miles and mode in Europe and Canada: <a href=\"compare.html\">US / Europe / Canada</a>."
    }
  ],
  "comparisons": [
    {
      "id": "gossling",
      "label": "Gössling et al. 2019",
      "place": "EU passenger-km",
      "note": "€0.11 per passenger-km external cost for cars (2017€). Different bag than Parry: infrastructure construction, parking land, roadway land, and climate are large. Private cost of the car is much larger (€0.85/pkm), mostly time.",
      "url": "https://doi.org/10.1016/j.ecolecon.2018.12.016"
    },
    {
      "id": "shoup",
      "label": "Shoup, The High Cost of Free Parking",
      "place": "United States",
      "note": "Off-street parking minimums and bundled “free” parking shift the cost of storing cars onto everyone who pays rent, prices, or taxes. Litman’s $0.20/mi is a compilation of that subsidy per vehicle-mile, not Shoup’s own per-mile table.",
      "url": "https://www.routledge.com/The-High-Cost-of-Free-Parking-Updated-Edition/Shoup/p/book/9781932364965"
    },
    {
      "id": "nhtsa",
      "label": "NHTSA crash social harm 2019",
      "place": "United States",
      "note": "Crashes that year: $340 billion economic cost, nearly $1.4 trillion including quality of life. That is on the order of 10¢ economic / 40¢ comprehensive per mile — most of it occupant harm, not Parry’s externality on strangers. If the crash line here looks small, that is why.",
      "url": "https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/813403"
    }
  ]
}