National Tunnel Inventory Risk Monitor — FHWA / NTAD

Screen every US road tunnel in the FHWA National Tunnel Inventory (NTI) — the official federal register of the 580 highway tunnels on public roads — and get back one clean row per tunnel with a composite 0-100 tunnel risk score and the routing-critical facts freight, hazmat, insurance and asset teams actually need: hazmat restriction, posted height restriction, load posting, and inspection status.

Data comes straight from the USDOT/BTS National Transportation Atlas Database (NTAD) ArcGIS service — keyless, authoritative, refreshed by FHWA. No login, no scraping.

Who it's for

• Freight & hazmat routing / TMS teams — pre-screen tunnels on a corridor for hazmat bans, posted height restrictions, low vertical clearance and posted load limits.
• Insurers & reinsurers — surface load-posted, closed or overdue-inspection tunnels in a book of infrastructure or transport risk.
• Infrastructure asset managers, DOT contractors & engineers — a ready-scored inventory by state, ranked worst-first, to triage inspection and rehab backlogs.
• Journalists & analysts — a defensible, sourced view of aging or restricted tunnels.

What it does

1. Runs a live drift probe against the NTAD layer before anything billable: the layer resolves, all 69 columns it reads still exist, the national count sits in band, the layer still carries exactly one inventory year, load-posting codes stay inside their closed A/P/R/K vocabulary, a positive canary returns tunnels, a negative control returns exactly zero, portal coordinates are decimal degrees, and the two restriction columns the product rests on are still populated. If any of that fails the run fails loudly and bills nothing.
2. Pulls tunnels for the states you choose (or the whole national inventory), paging with the service's own maxRecordCount and cross-checking the row count against the service's own returnCountOnly.
3. Normalizes every record: FIPS state code -> postal + full name, epoch-ms inspection dates -> YYYY-MM-DD, coded restriction fields -> booleans, all-9s sentinels -> null.
4. Computes a composite tunnel_risk_score (0-100) and boolean risk flags.
5. Sorts worst-first, assigns a risk_rank, caps to maxResults, and only then pushes.

Example input

{
  "states": ["CA"],
  "minRiskScore": 0,
  "maxResults": 2000
}

• states — postal codes ("CA"), full names ("California"), or 2-digit FIPS ("06"). Leave empty to scan the whole national inventory (580 tunnels).
• minRiskScore — optional 0-100 floor; only return tunnels at or above it.
• maxResults — safety cap; results are taken from the highest-risk end after ranking.

Three things this actor is careful about

1. Over-height routing needs the owner's flag, not just a measurement. NTI item L.10 is the owner-reported posted height restriction and it is set on 349 of 580 tunnels. A measurement-only test at 14 ft misses 182 of them — the Ted Williams and Eisenhower tunnels among them. over_height_routing_risk is a gated verdict that reads both the validated clearance and L.10, and is false only when both were checked and both are negative.

2. A published number is not automatically a fact. The NTI lists the Baltimore Harbor Tunnel at a minimum vertical clearance of 135 ft; MDTA posts it at 13'6". The published value is preserved verbatim in height_restriction, but min_vert_clearance_ft_validated is null, clearance_data_suspect is true, and no verdict is computed from it.

3. The NTI is an ANNUAL snapshot, so "overdue" needs an anchor. The layer carries a single inventory year and its newest reported inspection is 2025-02-20. Comparing that to today measures publication lag, not compliance — it puts 78.3% of the national inventory in "overdue" and climbs toward 100% on its own. overdue_inspection is therefore anchored to data_last_updated (49.7% of the inventory), with the run-time view kept beside it as overdue_inspection_as_of_today.

Output fields (one row per tunnel) — 96 fields

Field	Type	What it is
tunnel_number	string	FHWA NTI tunnel number (item I.1) - the tunnel's unique ID within its state.
tunnel_name	string	Common tunnel name (item I.2).
state	string	Full US state name, derived from the 2-digit FIPS state code (item I.3).
state_abbr	string	US state postal code, derived from the FIPS state code.
state_fips	string	2-digit FIPS state code exactly as stored in the NTI (item I.3).
county_code	string	3-digit county FIPS code (item I.4).
facility_carried	string	Road or facility carried through the tunnel (item I.10).
latitude	number	Decimal-degrees latitude of the tunnel portal (item I.13).
longitude	number	Decimal-degrees longitude of the tunnel portal (item I.14).
year_built	integer	Year the tunnel was built (item A.1).
year_rehabilitated	integer	Year of the last major rehabilitation (item A.2); null when never rehabilitated.
tunnel_length_ft	integer	Overall tunnel length in feet (item G.1).
adt	integer	Average daily traffic through the tunnel (item A.4). Reported for context only - it is NOT an input to tunnel_risk_score.
adtt	integer	Average daily truck traffic (item A.5).
adt_year	integer	Year the average daily traffic count was taken (item A.6).
owner	string	Owning agency decoded from the NTI owner code (item C.1).
last_inspection_date	string	Date of the last actual routine inspection (item D.2), ISO YYYY-MM-DD; null when none on record.
inspection_interval_months	integer	Designated routine inspection interval in months (item D.3), typically 24.
months_since_inspection	integer	Whole months elapsed between the last reported routine inspection and this run. Because the NTI is an annual snapshot this includes publication lag; months_since_inspection_at_vintage removes it.
inventory_load_rating_factor	number	Inventory-level load rating factor (item L.2). Below 1.0 indicates reduced capacity; 0 means not rated. Interpret alongside load_rating_method_code.
operating_load_rating_factor	number	Operating-level load rating factor (item L.3) - the structural-adequacy proxy in the risk score. Interpret alongside load_rating_method_code: 0 means not rated, and 65% of the inventory is method N with a 0 here.
posting_load_gross_tons	integer	Posted gross vehicle load limit in tons (item L.5) when the tunnel is load-posted. Null when not posted - NTI writes 0 for no posting and 99 as its all-9s "no limit" sentinel, and neither is emitted as a tonnage.
worst_condition_rating	string	Editorial condition label derived from load-rating factor and load-posting status (the NTI has no FHWA 0-9 component rating): Closed, Below Legal Load, Load Posted, Adequate, or Unknown.
load_posting_status	string	Decoded tunnel load posting status (item L.4): Open, no restriction / Posted for load / Posted (other than load) / Closed.
load_posting_code	string	Raw NTI load posting status letter (item L.4): A, P, R, or K.
hazmat_restricted	boolean	True when a hazardous-material routing restriction is in effect (item L.11). Null when the column was not returned - null means not checked, false means checked and negative.
height_restriction	number	Minimum vertical clearance over the tunnel roadway in FEET exactly as published (item G.2), including values that are not physically plausible. Use min_vert_clearance_ft_validated for a measurement you can act on, clearance_data_suspect to see which rows were rejected, and height_restriction_posted for the owner-reported restriction flag.
overdue_inspection	boolean	True when the last reported routine inspection was already older than the designated interval AS OF THE DATA VINTAGE (see data_last_updated and overdue_basis). The NTI is an annual snapshot, so comparing it to today measures publication lag rather than compliance - overdue_inspection_as_of_today carries that run-time view separately.
load_posted	boolean	True when the tunnel is legally posted for a reduced load (status P or R).
low_clearance	boolean	True when the VALIDATED minimum vertical clearance is below 14 ft (over-height hazard vs the ~13ft 6in statutory commercial height). Null - never false - when the clearance is missing or implausible. See over_height_routing_risk for the gated verdict that also reads the owner-reported item L.10 flag.
tunnel_risk_score	integer	Composite EDITORIAL screening score 0-100: condition proxy (operating load rating factor) x load-posting status x inspection staleness measured at the data vintage x restriction multiplier (hazmat, over-height, other). The NTI publishes no FHWA 0-9 condition rating, so this is a screening blend and not an official rating. ADT is not an input.
risk_flags	array	Machine-readable flags: overdue_inspection, closed, load_posted, below_legal_load, hazmat_restricted, low_clearance, height_restriction_posted, other_restrictions.
risk_rank	integer	1-based rank within this run's results, sorted by risk score descending (1 = highest risk).
source_url	string	NTAD ArcGIS query URL returning this tunnel's full raw NTI record.
checked_at	string	ISO 8601 timestamp of when this run read the NTI.
objectid	integer	Stable feature id within the NTAD National Tunnel Inventory layer.
data_vintage_year	integer	FHWA inventory year carried on the record itself. The layer holds exactly one year; two would double-count every tunnel and the run fails.
data_last_updated	string	ISO date the NTAD layer itself was last edited - the vintage every overdue verdict is anchored to.
county_fips	string	State FIPS + county FIPS concatenated, ready to join to Census county data.
next_inspection_target_date	string	Target date FHWA published for the reported routine inspection cycle (item D.1), ISO YYYY-MM-DD. This is the target for the inspection already reported, NOT a forward-looking next-due date.
months_since_inspection_at_vintage	integer	Whole months between the last reported routine inspection and the data vintage, with annual publication lag removed.
overdue_inspection_as_of_today	boolean	True when the last reported inspection is older than the interval measured against this run time. Grows toward true for the whole inventory as the annual snapshot ages - use overdue_inspection for the compliance read.
overdue_basis	string	Which clock overdue_inspection used: data_vintage (normal) or run_time (the layer stopped publishing an edit date).
height_restriction_posted	boolean	Owner-reported posted height restriction (item L.10) - the authoritative over-height signal, populated on 349 of 580 tunnels. Null when the column was not returned.
over_height_routing_risk	boolean	Gated over-height verdict: true when EITHER the validated clearance is below 14 ft OR the owner posts a height restriction; false only when both were checked and both are negative; null when neither could be checked.
min_vert_clearance_ft_validated	number	Item G.2 clearance in feet, or null when the published value is not a physically plausible tunnel clearance.
clearance_data_suspect	boolean	True when the published G.2 clearance is impossible (<=0 ft or >40 ft) and was therefore not used for any verdict.
other_restrictions	boolean	Item L.12 other-restrictions flag. Null when the column was not returned.
closed_to_traffic	boolean	True when the load-posting status (item L.4) is K, Closed. Null when the status was not returned.
below_legal_load	boolean	True when the operating load rating factor is above 0 and below 1.0. Null when no rating was returned.
load_rating_method_code	string	Raw item L.1 load-rating method code as published by FHWA. Essential context for the two rating-factor fields: 65% of the inventory is method N with a 0 rating.
total_lanes	integer	Total number of lanes through the tunnel (item A.3).
number_of_bores	integer	Number of tunnel bores (item S.1).
roadway_width_ft	number	Curb-to-curb roadway width in feet (item G.3).
left_sidewalk_width_ft	number	Left sidewalk width in feet (item G.4).
right_sidewalk_width_ft	number	Right sidewalk width in feet (item G.5).
detour_length_miles	integer	Detour length in miles (item A.7); null when FHWA writes its 999 sentinel.
service_in_tunnel_code	integer	Raw item A.8 code for what the tunnel carries, as published by FHWA.
direction_of_traffic_code	integer	Raw item C.3 traffic-direction code as published by FHWA.
toll_code	integer	Raw item C.4 toll code as published by FHWA.
nhs_route	boolean	True when the tunnel carries a National Highway System route (item C.5).
strahnet_route	boolean	True when the tunnel carries a Strategic Highway Network route (item C.6) - a defense-mobility corridor.
functional_classification_code	integer	Raw item C.7 functional-classification code as published by FHWA.
urban_code	integer	Census urban area code (item C.8); null when FHWA writes its 99998/99999 sentinels.
route_number	string	Route number carried through the tunnel (item I.7).
route_type_code	string	Raw item I.9 route-type code as published by FHWA.
route_direction_code	string	Raw item I.8 route-direction code as published by FHWA.
highway_district	string	State highway district (item I.6).
place_code	string	Census place code (item I.5).
lrs_route_id	string	Linear referencing system route identifier (item I.11), for joining to state roadway networks.
lrs_mile_point	number	Milepoint of the tunnel along the LRS route (item I.12).
federally_owned	boolean	True when a federal agency owns or reports the tunnel (federal_agency = Y).
operator	string	Operating agency decoded from the NTI operator code (item C.2) - often different from the owner.
under_navigable_waterway	boolean	True when the tunnel passes beneath a navigable waterway (item N.1).
navigable_waterway_clearance_ft	number	Vertical clearance over the tunnel to the navigable waterway (item N.2), feet.
portal_island_protection	boolean	True when the tunnel or its portal island has protection works (item N.3).
tunnel_shape_code	integer	Raw item S.2 tunnel-shape code as published by FHWA.
portal_shape_code	integer	Raw item S.3 portal-shape code as published by FHWA.
ground_conditions_code	integer	Raw item S.4 ground-conditions code as published by FHWA.
complex_tunnel	boolean	True when FHWA classifies the tunnel as complex (item S.5), which drives heightened inspection requirements.
in_depth_inspection_required	boolean	Item D.4 in-depth inspection requirement flag.
damage_inspection_required	boolean	Item D.5 damage inspection requirement flag.
special_inspection_required	boolean	Item D.6 special inspection requirement flag.
border_state	string	Partner state for a tunnel on a state border (item I.15), as published (postal or FIPS).
border_tunnel_number	string	Partner state tunnel number for a border tunnel (item I.17).
border_financial_responsibility_pct	integer	Share of financial responsibility for a border tunnel (item I.16), percent.
border_inspection_responsibility	string	Raw item I.18 code for which state inspects a border tunnel.
submitted_by	string	Agency code that submitted the record to FHWA.
nti_source_status	string	Outcome of the NTI fetch for this row: ok. A run where the source did not answer fails and emits nothing.
nti_layer_name	string	Name of the NTAD FeatureServer layer this run read.
nti_layer_feature_count	integer	Total tunnels in the layer at run time, from the service's own returnCountOnly.
matching_tunnel_count	integer	Tunnels matching your filter upstream, from the service's own returnCountOnly - the exact truncation guard.
result_truncated	boolean	True when maxResults capped the run below matching_tunnel_count.
tunnels_scanned	integer	How many tunnel records this run actually retrieved before filtering.
where_clause	string	The ArcGIS where clause this run sent, so the answer is reproducible.
drift_checks_passed	boolean	True when every live drift assertion passed before any row was emitted. A run cannot bill a row with this false.

How the tunnel risk score works (editorial model)

The NTI does not publish an FHWA 0-9 component condition rating like the National Bridge Inventory does, so tunnel_risk_score is an editorial screening blend — a triage aid, not an official FHWA rating. It multiplies four factors and normalizes so the worst realistic combination scores 100:

Factor	Signal	Source item
Condition proxy	operating load-rating factor (< 1.0 = below legal load)	L.3
Load posting	Open / Posted-for-load / Posted-other / Closed	L.4
Inspection staleness	months since inspection at the data vintage vs interval	D.2 / D.3
Restrictions	hazmat ban, over-height routing risk, other restrictions	L.10-L.12, G.2

adt is not an input to the score — it is reported for context only. worst_condition_rating is a matching human label (Closed / Below Legal Load / Load Posted / Adequate / Unknown). Read the two load-rating factors alongside load_rating_method_code: 65% of the inventory is method N with a 0 rating, which means not rated, not zero capacity.

What "null" means here

null means not checked. false means checked, and the answer is negative. Every restriction flag follows that contract, so an upstream column that stops publishing produces null rather than a confident clear. If the source cannot be reached at all, or a page of the query fails part-way, the run fails rather than emitting an arbitrary partial inventory ranked as though it were complete — nothing is emitted and nothing is billed. Every row also carries nti_source_status, matching_tunnel_count, result_truncated, tunnels_scanned, where_clause and drift_checks_passed so you can see exactly what the answer rests on.

Use as an MCP tool

This actor is a clean, chainable tool for AI agents (Claude, Cursor, etc.) via mcp.apify.com. Every input and output field is described in the schema, so an agent can call it directly — e.g. "list the hazmat-restricted or over-height tunnels in Colorado and Utah" — and get structured, ranked JSON back. Billing is unchanged when it is called as a tool, and a run that cannot answer fails without billing.

Pricing

Pay-per-result: one billable result per tunnel returned, with graduated volume discounts. A run that fails its drift check, or that could only retrieve a partial inventory, emits nothing and bills nothing.

FAQ

Where does the data come from? The FHWA National Tunnel Inventory, published in the USDOT/BTS National Transportation Atlas Database (NTAD) as a public ArcGIS FeatureServer. No API key required.

How many tunnels are there? 580 highway tunnels on US public roads nationwide (measured live 2026-08-10).

Is the risk score an official FHWA rating? No. It is an editorial screening blend of FHWA-published fields meant for triage. Always confirm against the primary record via source_url.

Why is overdue_inspection different from overdue_inspection_as_of_today? The NTI is published annually. The first answers "was this tunnel already past its interval when FHWA published?", the second "is it past its interval right now?" — which for an aging snapshot is mostly a statement about the publication schedule.

Does it cover rail or transit tunnels? No — the NTI covers highway/road tunnels on public roads and publicly accessible federal-land tunnels.

How is it billed? Pay-per-result: one billable result per tunnel returned. Empty results cost only the tiny actor start.

Related actors

• FHWA NBI Bridge Risk Monitor — the same treatment for the 620k-structure National Bridge Inventory, including FHWA's official 0-9 condition ratings and scour-critical screening.

Source

FHWA National Tunnel Inventory (NTI) via NTAD: https://services.arcgis.com/xOi1kZaI0eWDREZv/arcgis/rest/services/NTAD_National_Tunnel_Inventory/FeatureServer/0

Each field is a screening aid, not a determination. Confirm against the primary FHWA record before acting on any routing, insurance or engineering decision.