Category «Data»

Shielding and Weaponizing Your Travel Model

Excerpt from “The Planners Guide to Advocacy Modeling” by Alan Horowitz Chapter 12.  Shielding and Weaponizing Your Travel Model  Earlier chapters of this book describe methods of building and calibrating a travel model to assure that it produces the desired policy outputs.  However, a model will not be particularly useful in advancing a political agenda unless certain steps are taken to …

Six Short Essays on Highway Path Choice

Where are All the Trucks?  Getting Truck Costs Right Is Really Important  Several years ago, I was working with FAF (Freight Analysis Framework) truck assignment results for the upper Midwest.  Those early FAF assignments routed trucks according to travel time.  I noticed lots of trucks being assigned to the Chicago Skyway.  The Chicago Skyway is a short toll road that runs from the south side …

The Elusive Concept of Delay in Urban Traffic

I recently read a paper where the authors tried to compute a congestion index from ridesharing data for a city by comparing daytime average speeds to nighttime average speeds. While reading this paper I couldn’t help but to reflect on an experience I had while working at General Motors Research Laboratories decades ago. One GM …

Statistical Testing is Essential to Transportation Research

I have lately refereed journal submissions where authors have totally evaded the concept of a statistical test while trying to demonstrate the importance of their research.  I will give somewhat altered (to protect the identities of the authors and avoid lawsuits) examples later.  Mainly, each of these authors has developed an innovation, compared the innovation …

A Case for Balancing Traffic Counts with OD Table Estimation

Balancing of traffic counts is an attempt to eliminate errors due to lack of conservation of vehicles through intersections and interchanges.   My friends at the WisDOT swear by it. Most other traffic and travel modelers have never heard of it. One of my co-authors on NCHRP Report 765, Tom Creasey, was charged with writing up …

The Promises and Pitfalls of OD Table Estimation from Ground Counts

Estimating origin-destination (OD) tables from ground counts can be controversial.  In many cases the number of variables of the estimation problem greatly exceeds the number of data points.  This means that additional information must be gotten from somewhere, and the quality of that information is often suspect. QRS II contains many different methods for performing …