The island-wide trend
Traffic peaked in 2019.
It hasn't come back.
The 2015–2025 index uses only the road sections that have a value in every one of those eleven years, so each year is measured on the same roads. Many yearly values are estimates carried forward from an earlier count, so the share of sections actually counted each year is shown under the chart. Lower daily counts do not prove a road is less congested; peak-hour crowding, construction and lane capacity matter too.
The arteries
Corridor by corridor.
Click a corridor to isolate it on the map. Each column compares only the sections that have both of its years. Average AADT is weighted by length; it is not a total of vehicles.
| Corridor | Sections · miles | 2025 avg AADT | 2015–25 trend (2019=100) | 2025 vs 2019 | Recount vs pre-2020 | vs 2015 | vs earliest count |
|---|
Where the counts moved
Biggest gains. Biggest drops.
Ranked by the change in vehicles per day between the newest recount (2022–2025) and the last count taken in or before 2019. Ramps are excluded, and so is any section that never reached 3,000 vehicles/day. Very large jumps can come from a redrawn count section or a construction detour, so click a row and check its history before relying on it.
Top gainers
| Road / section | Δ vehicles/day | Δ % | Count years |
|---|
Top decliners
| Road / section | Δ vehicles/day | Δ % | Count years |
|---|
Town by town
Every town & city.
Length-weighted change on matched sections. Click a row to filter the map.
| Town / city | Sections (2019→2025) | 2025 vs 2019 | Up / down | Recount vs pre-2020 | vs 2015 | vs earliest count |
|---|
The filtered network
Every section, listed.
This table follows the map filters (county, town, corridor, search, ramps), sorted by 2025 volume. Missing values stay blank. Nothing is filled in.
| Road | Station | County · town | 2025 AADT | Last counted | vs 2019 | Recount Δ |
|---|
What's covered and what isn't
The gaps, stated plainly.
Bars show how many mapped sections were actually counted in each year. They are not traffic volumes. Counts before 2015 are sparse, and a missing year means the road wasn't counted that year. It does not mean there was no traffic.
Read before citing
Methodology.
What the numbers are
Each value is the official annual average daily traffic (AADT) for a numbered count section: the estimated average number of vehicles per day in both directions combined. Short counts, usually a few days long, are adjusted for season and day of week into an annual average. In years when a section isn't counted, the official yearly figure is the last count growth-factored forward, and it's flagged as an estimate. This map keeps that flag. Each road's inspector labels every value as counted or estimated.
The comparisons
- 2025 vs 2019 (default): the official 2025 AADT against the official 2019 AADT for the same section. 2019 is the last full year before COVID.
- Newest recount vs pre-2020 count: uses actual counts only, no estimates. It compares the latest count taken in 2022–2025 with the latest count taken in or before 2019. The exact years differ by road and are shown for each one. 2020–21 counts are left out so the pandemic low doesn't distort the endpoint.
- 2025 vs 2015: official AADT for both years. ~20 years: 2025 AADT against the actual count closest to 2005 (2002–2008). Earliest: 2025 AADT against the first count on record for that section before 2020, which can go back to 1977.
- Island, county, town and corridor totals:
Σ(AADT₂ × miles) ÷ Σ(AADT₁ × miles) − 1, using only non-ramp sections that have both values. That is a matched, length-weighted measure of vehicle-miles. It isn't a count of unique vehicles, and each comparison uses its own set of sections. - 2015–2025 index: the same calculation, run on a fixed set of non-ramp sections that have an official AADT in all eleven years, with 2019 set to 100.
Map geometry
Count sections are drawn from the official current station-section lines. A few sections that exist only in the 2025 AADT layer use that layer's geometry instead. Historical values are joined by station number. Section mileage is measured from the line geometry. Each section is assigned to the town or city containing its midpoint, so a road that crosses a town line appears in only one town. Corridor groupings come from route numbers and road names. Ramps and LIE service roads are kept as separate groups.
Known gaps and caveats
Mapped sections with full history (GeoJSON) · All sections, all years (CSV) · Summary tables (JSON)