How CMS actually measures time and distance.

Time and distance is the most commonly misunderstood component of Medicare Advantage network adequacy. Plans have a general sense that CMS measures how far members have to travel to see a provider, and that there are different standards for urban versus rural counties. The specific mechanics — which methodology CMS uses, which specialties have separate standards, how states layer their own requirements on top — are where surprises happen.

Drive time, not straight line

CMS network adequacy reviews use drive time, not straight-line distance. This distinction matters significantly in markets with geographic barriers — major interstates, rivers, mountainous terrain — where a provider who is five miles away as the crow flies might be a 45-minute drive. Plans that build their adequacy models using straight-line distance and assume they will pass the CMS review often find that their models overstate their coverage when CMS applies drive-time methodology.

The drive-time calculation CMS uses is based on the CMS Health Outcomes Survey zip code centroid methodology, applied against a commercial mapping service. It is not the same as Google Maps routing — the tool applies typical traffic conditions and road network data in a specific way that you need to understand if you are modeling your own adequacy before submission.

The urban/suburban/rural breakdown

CMS applies different standards based on county designation. The designations are set by the Rural-Urban Commuting Area (RUCA) codes:

• Urban: Primary care access within 30 minutes or 30 miles (whichever is shorter). For most specialists, the threshold is 30 minutes or 30 miles as well, with some specialties having longer standards.
• Suburban: Generally similar to urban, with some specialties at 30 minutes or 30 miles and others at 60 minutes or 60 miles.
• Rural: Standards are extended significantly — typically 60 minutes or 60 miles for primary care, with many specialty thresholds at 90 minutes or 90 miles. Some specialties have rural exceptions that allow plans to document that no provider is available within the standard radius.

These thresholds are applied at the county level using the member's residence ZIP code, not the provider's location. A provider located in an urban area who serves members in a rural county is evaluated against the rural standard for those members.

Specialty-specific thresholds

CMS publishes specialty-specific time and distance standards in the Medicare Advantage network adequacy guidelines, updated annually in the Call Letter. The standard thresholds apply to the primary specialties, but several categories have their own separate standards:

• Behavioral health: Has its own standards, which are increasingly being scrutinized given state and federal parity requirements. For some markets and plan types, telehealth can satisfy part of the behavioral health adequacy standard under specific conditions.
• Oncology: CMS has historically applied a longer acceptable drive-time standard for oncology, recognizing that patients and families are often willing to travel farther for cancer care.
• Hospital services:Inpatient hospital access is evaluated separately from physician access and has its own time-distance thresholds that don't always align with the physician specialty standards.

The percentage threshold problem

CMS does not require 100% of members to be within the time-distance standard for every specialty. It requires a certain percentage of members in each county to have access. For most specialties, that threshold is 85% to 90% of members. For primary care, it is higher.

This means you can pass the adequacy review with some members outside the standard — but the percentage calculation is applied county by county, not at the market level. A county that fails is a county that fails, regardless of how well your other counties perform. Plans that model adequacy at the market level and discover county-level failures at submission have a difficult problem to solve on a short timeline.

State layers on top of CMS

State DOI requirements do not replace CMS requirements — they layer on top. Several states have time-distance standards that are stricter than CMS for certain specialties or geographic designations. A plan that passes CMS network validation may still have to address state DOI adequacy questions before it can sell in that state.

The CMS review is not the only adequacy review you will face. State insurance departments have their own standards, their own timelines, and their own track records for how they apply them.

Before you finalize your adequacy model for any state, pull the relevant state insurance department guidance alongside the CMS standards. The standards don't always match, and the tighter of the two is the one that governs your compliance in that state.