Transportation Engineering Cheat Sheet

The core ideas of Transportation Engineering distilled into a single, scannable reference — perfect for review or quick lookup.

PiqCue — piqcue.com/transportation-engineering/cheatsheet

Quick Reference

Level of Service (LOS)

A qualitative measure of traffic operating conditions on a roadway or intersection, graded from A (free flow) to F (forced or breakdown flow), used to evaluate and design transportation facilities.

Highway Capacity

The maximum sustainable flow rate at which vehicles can traverse a point or section of roadway during a specified time period under prevailing conditions, typically expressed in passenger cars per hour per lane (pc/h/ln).

Geometric Design

The engineering design of the visible features of a roadway, including horizontal and vertical alignment, cross-section elements, sight distances, and intersection configurations, to ensure safety and operational efficiency.

Pavement Design

The engineering process of determining the thickness and material composition of pavement layers (surface, base, subbase) to withstand anticipated traffic loads and environmental conditions over the design life.

Traffic Signal Timing

The process of determining the allocation of green, yellow, and red intervals for each phase of a traffic signal to optimize throughput, minimize delay, and ensure safe clearance of conflicting movements.

Sight Distance

The length of roadway visible to a driver, critical for safe operations. Types include stopping sight distance, passing sight distance, and decision sight distance, each calculated based on design speed and driver reaction time.

Intelligent Transportation Systems (ITS)

The application of advanced technologies including sensors, communications, and computing to transportation infrastructure and vehicles to improve safety, efficiency, and sustainability of transportation networks.

Traffic Flow Theory

The mathematical study of the relationships among traffic flow (vehicles per hour), density (vehicles per mile), and speed, described by the fundamental equation: flow equals density times speed (q = k * u).

Superelevation

The banking or tilting of the roadway surface on a horizontal curve to counteract the centrifugal force on vehicles, helping them maintain their lane at the design speed without relying solely on tire friction.

Equivalent Single Axle Load (ESAL)

A standardized measure of pavement damage caused by vehicle axle loads, converting the damaging effect of any axle configuration and weight to the equivalent effect of a standard 18,000-pound single axle load.

Key Terms at a Glance

AASHTO:The American Association of State Highway and Transportation Officials, which publishes design standards and guidelines for highways and bridges in the United States.

Average Daily Traffic (ADT):The total volume of traffic passing a point or segment of a highway in both directions over a 24-hour period, averaged over a year.

California Bearing Ratio:A soil strength test comparing penetration resistance of a sample to that of standard crushed stone, used in pavement design.

Complete Streets:Streets designed to accommodate all users including motorists, transit riders, bicyclists, and pedestrians safely.

Connected and Autonomous Vehicles:Vehicles with communication (V2V, V2I) and/or automated driving capabilities that will reshape transportation infrastructure.

Critical Density:The traffic density at which flow reaches its maximum (capacity). Beyond this point, congestion occurs.

Design Speed:The maximum safe speed for a roadway section under favorable conditions, governing geometric feature selection.

Equivalent Single Axle Load:A standard unit quantifying pavement damage from vehicle axle loads relative to an 18,000-pound single axle.

Flexible Pavement:Pavement using asphalt layers over aggregate base, distributing loads through the layer system.

Geometric Design:The design of roadway physical features including alignment, cross-section, sight distance, and intersection layout.

Highway Capacity:The maximum sustainable traffic flow rate on a roadway under prevailing conditions.

Highway Capacity Manual:The TRB publication providing standard methodologies for evaluating highway and street operations and level of service.

Intelligent Transportation Systems:The application of advanced technologies to transportation for real-time monitoring, control, and communication.

Level of Service:A qualitative measure of traffic conditions graded A (free flow) through F (breakdown), used to evaluate facility performance.

Pavement Design:The engineering process of determining pavement layer thicknesses and materials to withstand traffic and environmental loads.

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