One of the most common questions in traffic impact assessments (TIAs) is whether to propose turning lanes, acceleration lanes, or deceleration lanes. While adding lanes may seem like a straightforward solution to congestion, proposing them without justification can create unnecessary cost, invite reviewer comments, or even compromise safety. In this post, we’ll explain when to […]
Road classification (or class) is a fundamental concept in transportation planning and traffic engineering. It provides a framework for organizing roads according to their function within the transportation network, specifically how they balance mobility (moving traffic efficiently) and access (serving adjacent land uses). Higher-class roads prioritize mobility, moving large volumes of traffic over longer distances
Designing streets and highways requires careful attention to geometric standards. Lane widths, sidewalk sizes, medians, and other roadway elements affect safety, efficiency, and comfort. This guide provides a comprehensive reference for planners and traffic engineers, including typical dimensions for freeways, arterials, collectors, and local streets. All dimensions are shown in meters and feet, based on
What is an ESAL? ESAL Formula Where: Typical Load Equivalency Factors (LEFs) (based on AASHTO & typical LEFs) Vehicle Type Axles Typical Load (kips per axle) Approx. ESAL per Pass Passenger Car (sedan) 2 2–3 0.0004 Pickup / SUV 2 3–4 0.001 Delivery Van (2-axle, light) 2 4–5 0.005 Single-Unit Truck (2-axle, 6-tire) 2 6–9
A transportation (travel demand) model is a quantitative framework that forecasts how people and goods move through a region under different land-use and network scenarios. Done well, a model becomes a decision engine: it helps test road and transit projects, pricing policies, and growth plans before spending real money. This guide covers when you actually
Sight distance is one of the most important considerations in road design. It represents the length of roadway visible to a driver, ensuring there is enough distance to perceive, react, and stop safely when encountering obstacles or conflicts. Inadequate sight distance can lead to unsafe conditions, higher crash risks, and poor traffic flow. This reference
When planning a new road, street, or highway, one of the most important decisions you’ll face is whether to use flexible or rigid pavement. Each has its advantages, costs, and ideal use cases. Choosing the right type of pavement can save millions in construction and maintenance over the project’s lifecycle. In this post, we break
