Glossary

The terms that come up most often in road condition, traffic survey, enforcement and site safety work, in plain language.

Road condition

AADT (Annual Average Daily Traffic): The average number of vehicles using a road per day across a full year, used for planning and capacity work.
Alligator cracking: Interconnected cracks forming a pattern like crocodile skin, usually a sign of structural fatigue rather than a surface problem.
Chainage: Distance measured along a road from a fixed starting point, used to locate a defect or asset precisely.
Edge failure: Breaking away of the pavement at its outer edge, common where the shoulder is weak or unsupported.
IRI (International Roughness Index): A standard measure of how rough a road surface is, derived from the road's profile.
PCI (Pavement Condition Index): A 0–100 score describing pavement condition, calculated from the type, severity and extent of the distress present.
Ravelling: Loss of surface aggregate, leaving the road coarse and eventually pitted.
Retroreflectivity: How well a sign or road marking returns light to a driver's headlights, which is what makes it visible at night.
Rutting: Depressions in the wheel paths, formed by repeated loading.

Classified volume count (CVC): A count of vehicles passing a point, separated by vehicle type.
CVPD (Commercial Vehicles Per Day): The daily count of commercial vehicles, used in pavement design and toll assessment.
PCU (Passenger Car Unit): A conversion factor that expresses different vehicle types in terms of an equivalent number of cars.
Peak hour factor: The peak-hour volume divided by four times the busiest fifteen-minute interval within it, describing how evenly traffic arrives.
Turning movement count (TMC): A junction count recording each turning movement separately, rather than total volume.

ANPR (Automatic Number Plate Recognition): Reading vehicle number plates automatically from camera images.
Evidence package: The clip, frames and metadata assembled for a detected violation, so a case can be reviewed before any action is taken.
ICCC (Integrated Command and Control Centre): A city's central facility where traffic, surveillance and civic systems are monitored together.
RLVD (Red Light Violation Detection): Detecting vehicles that cross a stop line after the signal has turned red.

BOT (Build–Operate–Transfer): A concession model where a private party builds and operates a road, then transfers it back.
Defect liability period: The period after construction during which the contractor must repair defects at their own cost.
HAM (Hybrid Annuity Model): An Indian road contracting model splitting the cost between government funding and private investment repaid through annuities.
Independent Engineer (IE): The engineer appointed to monitor a concession independently of both the authority and the concessionaire.
TOT (Toll–Operate–Transfer): A model where an operator pays for the right to collect tolls on an existing road for a fixed term.

False positive: An alert raised for something that did not actually happen; the rate matters more than headline accuracy in day-to-day operations.
PPE compliance: Whether workers are wearing the required protective equipment, such as helmets and high-visibility vests.
Virtual boundary: A line or zone drawn on a camera view that triggers an alert when crossed.