OverviewDataset Summary
The complete VDOT-monitored road network of Northern Virginia: 29,156 bidirectional Average Daily Traffic segments totaling 11,137 km, carrying an estimated 106.6 million daily vehicle-miles traveled (DVMT). Each segment includes ADT, annual average weekday traffic (AAWDT), design-hour K-factor, and a six-class vehicle breakdown from which daily VMT, combined truck share, and truck VMT are derived per segment. The interactive map shows all 2,707 segments with ADT of 10,000 or more, colored by volume class, with DBSCAN freight cluster markers on top.
Why This DatasetThe Problem It Solves
Traffic volume data is the most requested input in local transportation work, yet VDOT publishes it as a statewide layer with no jurisdiction totals, no VMT, and no truck synthesis. This atlas clips the 2025 vintage to the exact 9-jurisdiction NoVA boundary, splits segments at borders so jurisdiction VMT sums are correct, and converts class percentages into truck vehicle-miles - the quantity that actually drives pavement wear, freight planning, and emissions models. The result is a regional freight geography: interstates carry 41.4% of all travel on 1.3% of segments, and Prince William County emerges as the region's truck jurisdiction with a 4.96% truck share of DVMT.
MethodologyHow It Was Built
The VDOT Bidirectional Traffic Volume 2025 layer (ADT with vehicle classification) was queried from the VDOT ArcGIS FeatureServer by bounding-box envelope with pagination (16 requests, 30,702 raw segments, EPSG:4326). Segments were overlay-intersected with TIGER/Line 2023 boundaries for the 9 NoVA jurisdictions (FIPS 51013, 51059, 51107, 51153, 51510, 51600, 51610, 51683, 51685), splitting segments at borders and yielding 29,156 clipped segments. Segment lengths were computed in EPSG:32618; daily VMT = ADT x length in miles; combined truck share = sum of 2-axle, 3-axle, single-trailer and double-trailer class percentages; truck DVMT = DVMT x truck share. High-truck segments (ADT >= 5,000 and truck share >= 8%; n=91) were reduced to representative points and clustered with haversine DBSCAN (eps=1,500 m, min_samples=5), resolving 3 freight corridor clusters with 62 isolated segments. FGDC metadata is embedded in both GeoPackages with XML sidecars. Anomaly detection and composite indexing were not run: the layer is a single-vintage network snapshot without a per-feature time series, and an index would duplicate the direct ADT/truck-share measures.
Key FindingsWhat the Data Shows
- 106.6 million daily vehicle-miles traveled: the 29,156 VDOT-monitored segments across the 9 NoVA jurisdictions carry 106.6M DVMT; Fairfax County alone accounts for 55.6M (52%).
- Interstates carry 41.4% of DVMT on 1.3% of segments: just 386 interstate segments handle over two-fifths of regional travel. The busiest segment is I-95S near Backlick Rd/Fairfax County Pkwy at 254,000 ADT; I-495 at the GW Memorial Parkway carries 246,000.
- Prince William County is the region's freight jurisdiction: highest truck share of DVMT (4.96%) and 1.10M daily truck-miles, driven by I-95, I-66 and VA-28 corridors.
- 3 DBSCAN freight corridor clusters: among 91 high-truck segments (ADT >= 5,000 and truck share >= 8%), clustering resolves two I-95 corridor clusters in southern Fairfax County (14 and 5 segments, 4.0M combined DVMT) and one Prince William cluster on the SC-621 corridor (10 segments, 9.7% mean truck share).
- The extreme truck outlier is a secondary road: SC-600 in Fairfax County (Furnace Rd near the Lorton landfill complex) runs 27.1% trucks on 9,000 ADT - a waste-hauling corridor invisible in interstate-focused freight planning.
- Urban compact cities post outsized intensity: Alexandria carries 4.5M DVMT on just 202 km (22,300 veh-mi per km), versus 10,060 per km in Fairfax County and 5,775 in Loudoun.
Analytical UsesWhat You Can Do With This
- Freight and logistics siting: truck-share segment data identifies corridors where warehouse, distribution and data center construction traffic concentrates.
- Pavement management: truck DVMT is the primary driver of pavement deterioration; the per-segment truck-mile estimates support lifecycle cost models.
- Traffic impact studies: baseline ADT/AAWDT with K-factors for development impact analyses required by county ordinances.
- Safety screening: joining crash datasets (e.g. the Day 34 VRU atlas) to ADT exposes crash-rate-per-vehicle outliers rather than raw counts.
- Air quality and noise modeling: segment-level VMT and truck mix feed MOVES emissions and FHWA TNM noise models.
Synthesis OpportunitiesWhat It Combines With
Join the Day 34 VRU crash atlas to compute crash rates per million vehicle-miles - exposure-normalized safety screening. Overlay the Day 33 power grid and data center atlas to quantify construction and service truck loading on the Loudoun/Prince William data center corridors. Combine with the Day 38 bus frequency atlas to contrast person-throughput of frequent bus corridors against general traffic. ADT also feeds FHWA TNM noise buffers around the Day 26 school locations.
LimitationsKnown Caveats
- Single vintage: the 2025 layer mixes count dates (DATA_DATE spans 1986-2025); low-volume secondary roads may carry older factored estimates rather than fresh counts.
- Estimated vs counted: ADT_QUALITY distinguishes actual counts from estimates; many secondary segments are estimates grown from older counts.
- Bidirectional totals: volumes are two-way; directional splits require applying DIRECTION_FACTOR.
- Coverage: VDOT monitors interstates, primaries and most secondaries but not local streets; Arlington maintains its own local network, thinning coverage there.
- Border splitting: overlay clipping splits segments at jurisdiction lines; segment counts are not comparable to VDOT statewide segment counts.
Data DictionaryFields in the GeoPackage
| Field | Type | Description | Units | Null OK? |
|---|---|---|---|---|
| ROUTE_COMMON_NAME | Text | VDOT route common name with direction | - | No |
| START_LABEL / END_LABEL | Text | Segment start and end descriptions | - | Yes |
| ADT | Real | Average Daily Traffic, two-way | vehicles/day | No |
| ADT_QUALITY | Text | Count vs estimate quality code | - | Yes |
| AAWDT | Real | Annual average weekday traffic | vehicles/day | Yes |
| PERCENT_* | Real | Vehicle class shares (4-tire, bus, 4 truck classes) | percent | Yes |
| K_FACTOR | Real | Design-hour factor | ratio | Yes |
| DIRECTION_FACTOR | Real | Peak directional split | ratio | Yes |
| RTE_TYPE_CD | Text | Route type (IS/US/SR/SC/ST/FR/OT) | - | No |
| jurisdiction / geoid | Text | NoVA jurisdiction name and FIPS | - | No |
| seg_km | Real | Clipped segment length (EPSG:32618) | km | No |
| truck_pct | Real | Combined truck share (4 classes) | percent | No |
| dvmt / truck_dvmt | Real | Daily vehicle-miles and truck vehicle-miles | veh-mi/day | No |
| cluster | Integer | DBSCAN freight cluster ID (-1 = isolated; clusters GPKG) | - | No |
Jurisdiction BreakdownResults by Jurisdiction
| Jurisdiction | Segments | Length (km) | Daily VMT | Truck DVMT Share | Max ADT |
|---|---|---|---|---|---|
| Fairfax County | 18,441 | 5,530 | 55.6M | 2.94% | 254,000 |
| Prince William County | 5,635 | 2,368 | 22.2M | 4.96% | 220,000 |
| Loudoun County | 3,847 | 2,458 | 14.2M | 2.48% | 161,000 |
| Arlington County | 600 | 397 | 8.3M | 2.59% | 194,000 |
| Alexandria City | 313 | 202 | 4.5M | 3.66% | 236,000 |
| Manassas City | 107 | 84 | 0.78M | 2.61% | 49,000 |
| Fairfax City | 91 | 52 | 0.70M | 1.23% | 36,000 |
| Falls Church City | 85 | 26 | 0.17M | 1.68% | 30,000 |
| Manassas Park City | 37 | 21 | 0.16M | 1.37% | 49,000 |
Sources & CitationsAll Data is Openly Licensed
- [1]Virginia Department of Transportation, Bidirectional Traffic Volume 2025 (ADT with Vehicle Classification), ArcGIS FeatureServer, accessed July 3, 2026.
- [2]U.S. Census Bureau, TIGER/Line Shapefiles 2023, County Boundaries.
- [3]Keystone GIS derived products: segment DVMT, truck DVMT, DBSCAN freight clusters (eps=1500 m, min_samples=5). CC BY 4.0.