Reading AADT traffic counts before choosing a retail site

AADT is annual average daily traffic: a measure of vehicle volume on a road over a year, expressed as a daily average. It helps describe a corridor's traffic, but it does not tell you how many customers can turn into a particular retail site. Before ranking parcels by AADT, check the count location, reporting year, direction, and access to the proposed entrance.

FHWA defines the measure in its Traffic Monitoring Guide glossary. Its federal reporting guidance calls for both directions to be included for two-way roads, with directional reporting for one-way roads, couplets, and ramps. Read the dataset's own notes before assuming the number beside a parcel represents traffic passing its driveway in one direction. FHWA reporting guidance

Check what the number actually measures

Find the source record behind the listing or map label. Record the station or segment ID, count year, direction covered, and whether the value is AADT or a shorter observed count.

The distinction between an annual estimate and a short count matters. FHWA describes adjustments that turn short-duration observations into AADT estimates, accounting for traffic patterns across time. A raw count from a particular Tuesday is a different measurement from the resulting annual daily average. FHWA traffic-data methods

For a site comparison, use the following questions as a research check:

• Does the station represent the road segment at the entrance, or a segment beyond a major intersection?
• Do both sites use the same reporting year and measurement type?
• Is the figure for the main road, a frontage road, a ramp, or one direction only?
• Has a road project or new connection changed the route since the observation?
• Is hourly or directional data available for the period the proposed business cares about?

If the count dates differ, leave that difference visible. Do not manufacture a current estimate by applying an assumed growth rate.

A worked example: the larger count leaves more unanswered

Consider two hypothetical sites for a morning-oriented retail business. All figures and road conditions below are illustrative, not observations of real properties.

Site A sits on a road with 40,000 AADT. The proposed parcel is beside the westbound lanes. During the selected morning hour, a separate directional count shows 2,000 eastbound movements and 800 westbound movements. A raised median prevents a direct left turn into the site from the eastbound lanes.

Site B sits on a road with 24,000 AADT. A count for the same morning hour shows 900 eastbound movements and 1,100 westbound movements. Its proposed entrance is also beside the westbound lanes.

On daily volume, Site A's road is about 67% busier: 40,000 divided by 24,000 is approximately 1.67. During the chosen morning hour, however, Site B has 37.5% more westbound movements: the difference of 300 divided by Site A's 800.

Those calculations answer two narrow questions. They do not prove Site B will sell more coffee, establish either site's capture rate, or show that every westbound driver can safely enter. They identify what to investigate next: the entrance location and queue at each site, the routes available to opposing traffic, and whether those routes work for the intended visit.

The hourly counts in this example are separate inputs. They were not derived by dividing AADT by 24 or by assuming half the traffic travels in each direction.

Trace a complete visit through the site

Start with a specific trip: a westbound commuter arriving during the morning peak, for example. Trace the approach to the entrance, the intended circulation through the property, and the exit back to the desired route. Then repeat for the opposing direction.

Record any median, permitted turn, signal, shared driveway, or off-site connection the route depends on. Where a proposed path crosses another property, identify the documentation needed to establish that access. An aerial image can help locate a visible driveway; it cannot establish the rights or approval supporting your proposed use of it.

For a concrete jurisdictional example, TxDOT requires a permit process to construct or revise a driveway connecting to its highway right of way. Its manual directs applicants to the local district and notes that some local agencies have delegated permitting authority. These are Texas state-highway procedures, not a national rule for every road. TxDOT driveway permits

Ask the responsible road authority about the proposed entrance before treating it as settled. A traffic engineer can then evaluate the operating questions the desktop review cannot answer. A lower daily count with a documented access plan and a higher daily count with unresolved access deserve different notes in the comparison.

Keep a short traffic-and-access worksheet

Use this suggested record for each parcel. It is a research worksheet, not an engineering calculation or an approval test.

Site address and parcel ID:
Proposed business and relevant operating period:

Traffic source and link:
Station / road segment:
Reporting year and date retrieved:
Metric: AADT / observed daily / hourly / other
Directions included:
Count value and units:
Relevant hourly or directional evidence:
Known road changes since the count:

Proposed entrance and exit:
Approach route from each direction:
Median and turn restrictions to verify:
Shared or off-site access documents needed:
Road authority and contact:
Permit or engineering review status:

Unanswered question that could change the decision:
Next action and responsible person:

Do not add counts from both roads at a corner and label the sum "unique customers." The figures count vehicle movements at their measurement locations, and the same trip can pass both locations. Neither figure establishes purchase intent.

Advance the question the data leaves open

Use AADT as one input to the retail site research brief. Once two candidates survive the first screen, make the unresolved access question explicit: for example, whether the proposed exit works during the intended operating period, or whether a shared entrance can be used as assumed.

Complete the remaining desktop site checks before advancing either parcel. The useful result is a comparison someone else can verify: the count source, the route being evaluated, and the specific approval or observation still needed.