Getting Started

Sequencing, Tools, and Data
The analyses will follow this sequence: 1) basic freeway sections, 2) interchanges, 3) weaving analyses, 4) ramps, and 5) Alternate Route 7 in both directions, as a freeway system as defined by the HCM. We will use a simulation model to look at all the facilities as a system.

In choosing the tools to use, you should pick those that strike a balance between the amount of effort they require and the amount of insight they provide. In this case study, we’re going to use two tools: 1) the HCM for all of the intersection analyses and the location-specific analyses at the freeway interchange; 2) VISSIM for a micro-simulation-based analysis of the entire network, to help us understand the interplay between the various facilities and add more detail.

Since the main purpose of this Guidebook is to illustrate how the HCM can be used to study traffic issues, we’ll use that tool wherever possible. We’ll also talk about where it isn’t applicable, explain why, and show you other tools that can be used.

We will need two types of data: 1) facility-related information (e.g., number of lanes, lane widths, lane configurations, saturation flow rates) and 2) traffic-related information (e.g., vehicular volumes and demands). We’ll show the specific data required for each problem as that problem is presented. We also need to know how NYSDOT designs highway facilities and the expectations it has for operational details. When we reach the system-wide level of analysis, we need to know simulation model inputs, such as lane changing and car following behavior as well as the origin-to-destination flow patterns.