Pavement Distress Survey

A pavement distress survey is an inspection that records the type, severity and quantity of every distress on a pavement. ASTM D5340 gives the method for airport pavement. ASTM D6433 gives it for roads and parking lots.

What it records

ASTM D5340 defines a pavement distress as an external indicator of deterioration. Loading, the environment or construction deficiencies cause it. Cracks, rutting and weathering are typical examples. The PAVER manuals list 17 asphalt distress types (codes 41 to 57) and 16 concrete distress types (codes 61 to 76). Most have a low, medium or high severity level. The inspector measures the quantity of each distress at each severity level in square feet or linear feet.

How an airport survey works

The pavement is divided into sections. A section has uniform construction, maintenance, usage history and condition. Each section is divided into sample units. An asphalt sample unit is 5,000 square feet, plus or minus 2,000. A concrete sample unit is 20 slabs, plus or minus 8.

The inspector walks each sample unit chosen. The inspector sketches it, measures its size with a hand odometer and records every distress. The inspector measures to 0.1 ft (30 mm). Traffic and aircraft noise are hazards. The survey must be coordinated with airport operations staff, and hearing protection must be available.

Sampling

The standard allows all sample units, enough for a 95 percent confidence level, or fewer. Surveying all of them is desirable for project analysis but is usually precluded for routine management by manpower, funds and time. Additional sample units are inspected only when a unit has an unusual distress, such as a utility cut.

From survey to PCI

Each distress quantity becomes a density. Deduct value curves turn each density and severity into a deduct value. The deduct values combine into a maximum corrected deduct value, and PCI = 100 - maximum corrected deduct value. The PCI of a section is the average of its surveyed sample units. The scale runs from 0 (failed) to 100 (new pavement).

The PCI is based on surface distress. It does not measure structural capacity, skid resistance or roughness.

Drones

FAA research flew small drones at six airports in 2020 and 2021. RGB images showed 13 of 14 concrete distresses and 6 of 9 asphalt distresses. Drone PCI values were close to those of the foot-on-ground inspection. The report recommends RGB images at 1.5 mm per pixel. Elevation models helped confirm faulting and shoving. A walked survey stays the reference.

Frequently Asked Questions

How often must an airport survey its pavement?

A federally obligated airport must do a detailed inspection of its airfield pavements at least once a year. If it performs a PCI survey to ASTM D5340, the detailed inspections by PCI survey may be extended to three years. These inspections are in addition to the routine maintenance inspections.

How many sample units must be surveyed?

ASTM D5340 allows all of them, enough for a 95 percent confidence level, or fewer. The formula for 95 percent confidence is n = N s squared / ((e squared / 4)(N - 1) + s squared). For a section of 20 sample units, with s = 10 and e = 5, it gives about 9.1, so at least 10 units.

Can a drone replace a walked survey?

Not in full. An FAA study flew drones at six airports in 2020 and 2021. RGB images showed 13 of 14 concrete distresses and 6 of 9 asphalt distresses. The drone PCI values were close to the foot-on-ground values. The report recommends 1.5 mm per pixel for the RGB images.

What does a distress survey not measure?

The PCI that comes from it cannot measure structural capacity. It also gives no direct measure of skid resistance or roughness. FAA AC 150/5320-6G calls the PCI a visual rating. To find the cause of a distress, you need more investigation.

This is a reference entry. TarmacView provides drone inspection services and doesn't sell the equipment or materials described in this glossary.

What is a Pavement Distress Survey?