Highway and Traffic Engineering: Transport Infrastructure Engineering

Practice flashcards covering core vocabulary and concepts from the Transport Infrastructure Engineering lecture on road design principles, classification, and alignment.

Road Design

The art of creating a 3D structure which should ideally be safe, efficient, functional, economical, and aesthetically pleasing.

Desired Speed

The speed at which a driver wishes to travel, determined by a combination of motivation and comfort.

Design Speed

The speed selected as a safe basis to establish appropriate geometric design elements for a particular section of road, logical with respect to topography and anticipated operating speed.

Operating Speed

Observed speeds during free flow conditions, which are generally lower than desired speed because operating conditions are not usually ideal.

Running Speed

The average speed maintained over a given route while a vehicle is in motion; the difference between this and design speed is strongly affected by traffic volumes.

Posted Speed

A speed limitation set for reasons of safe traffic operations rather than for geometric design considerations, aimed at encouraging drivers to travel at appropriate speeds.

Design Vehicle

A vehicle whose physical characteristics control the design and define several geometric design elements; types include passenger cars, buses, and various articulated trucks.

Passing Sight Distance

The distance required for the passing manoeuvre on substantial portions of the length of two-lane roads.

Intersection Sight Distance

The distance required to allow a driver on a minor road to evaluate whether it is safe to cross or enter the opposing stream of traffic.

Decision Sight Distance

The distance required for a driver to detect an unexpected hazard, recognize its potential threat, select an appropriate speed and path, and complete a safety manoeuvre.

Stopping Sight Distance (SSD)

The sum of the distance traversed from the instant a driver sights an obstruction to the instant brakes are applied (brake reaction distance) and the distance required to stop the vehicle.

Brake Reaction Time

The time interval assumed to be $2.5\,s$ for level terrain stopping calculations.

Functional Classification

A tool used to subdivide a complex network of roads into groups having similar characteristics for planning and geometric design control.

Design Domain Concept

A concept recognizing that there is a range of values for a design parameter between specific upper and lower levels that provide acceptable performance in term of safety, operation, and cost.

Road Safety Audit

A formal process aimed at minimizing the severity and risk of traffic crashes influenced by the road facility or adjacent environment.

Value Engineering

A management technique based on an intensive, systematic, and creative study to seek the best functional balance between project cost, reliability, and performance.

Horizontal Alignment

The plan view of a road consisting of tangents, circular curves, and transitions.

Vertical Alignment

The profile view of a road, consisting of tangent grades (straight lines) and vertical curves (crests or sags).

Stationing

A method of measuring distance where each station consists of $1000\,m$ (e.g., station $1+500$ is $1500\,m$ from origin).

Crest Vertical Curve

A vertical curve connecting an initial positive grade to a final negative grade, making a convex shape.

Sag Vertical Curve

A vertical curve connecting an initial negative grade to a final positive grade, making a concave shape.

K-value

The horizontal distance in metres required to affect a $1\%$ change in the slope of a vertical curve ($K = L/A$).

Superelevation

The inclination of the roadway toward the centre of a horizontal curve to counteract the centripetal acceleration produced as a vehicle rounds the curve.

Tangent Runoff

The length of road required to rotate a constant crossfall road from normal camber to level ($0\%$ cross-fall).

Superelevation Runoff

The length of road required to rotate the road from level ($0\%$ cross-fall) to the maximum superelevation rate.

Road Prism

The portion of the cross-section that includes the roadbed and transition slopes (cut or fill).

Traveled Way

The portion of the roadway for the movement of vehicles, which excludes the shoulders and medians.