book reviews

### Principles of Highway Engineering and Traffic Analysis, 4th ed. by Mannering, Washburn, and Kilareski

great book to read while you're driving down the highway ignoring the traffic regulations is Principles of Highway Engineering and Traffic Analysis. It's a basic introduction to what may be the most underappreciated branch of civil engineering: highway design. Calculating things like free-flow speed and maximum delay per vehicle is also an ideal way to pass the time when you get tired of talking on your cell phone and swearing at the guy in front of you.

It might come as a shock to many people, especially in the eastern United States, to discover that highways are designed. Yet it's true. Somebody actually thought it would be a good idea to eliminate the breakdown lane and fence in a 10-mile stretch of highway with car-scraping Jersey barriers, as was done in one highway, and to build a road that suddenly dives underneath another one like a roller coaster and comes back up just as suddenly--right before a stop light, as was done on another. To modern drivers, the photos of highways with only two or three cars in sight look like something out of the 1950s. (I could swear the car on the left on page 178 is a Studebaker.)

After a brief discussion of vehicle performance and braking, the book discusses the physical and geometric design of highways. For instance, there are formulas for line-of-sight distance vs. curvature and for how thick a pavement has to be to handle a certain traffic load. Next is queuing theory. Queuing theory is useful in explaining why, if a toll booth takes 15 seconds per vehicle, the average wait can be ten minutes or more. It's also useful in estimating how long you'll be stuck in a K-Mart when one cash register is doing a price check and the other 23 registers are closed due to a sudden massive six-hour coffee break. There are formulas for calculating yellow light times and optimal signal phasing. The book doesn't cover drainage, lighting, bridges, tunnels, or the effects of rain, darkness, or speed cameras, or how to site, build or maintain highways.

Chapter 6 discusses highway capacity, where queuing theory meets something called "level of service analysis." Readers will be most familiar with highways that this book would classify as "Level of Service F," which means exactly what it sounds like. On such roads, and I'm not exaggerating here, the average speed during "rush hour" is around 5 mph in clear weather, and 0.5 mph when it's raining or snowing. Unfortunately, the equations in the book don't apply to these traffic abominations, and this category is omitted from the tables, which consider 40 mph in a two-lane highway to be "congested." Snort!

There are many tables and meticulously explained worked examples throughout the book. The examples are US-centric, using English units. Most of the example problems and the problems at the end of each chapter are repeated in an appendix with metric units. Some calculus is used.

Jan 28, 2011

Apr 29, 2012