Amazon takes public transportation for its employees very seriously. So much so that the company says it has spent $60 million on public transit in Seattle. And the investment continues: Along with paying $5.5 million toward Seattle's streetcar in 2012, the retailer announced last week that it would invest $1.5 million to increase bus service to its headquarters.

That very big commitment to public transportation sheds some light on Amazon's eagerly awaited choice for "HQ2"--the home of its secondary headquarters after Seattle. According to Amazon's RFP, there are a few things the ecommerce giant really wants for its new home, besides an appropriate building site. These include: a population center no more than 30 miles away, an international airport no more than about 45 minutes away, one or more major highways or "arterial roads" no more than 1 to 2 miles away, and mass transit available at the site.

Apparently, Amazon is very, very serious about that last requirement. When the company announced its 20 finalist cities (out of 238 applicants) in January, some likely candidates, including Phoenix and Detroit, were absent from the list. Although they may have had other factors going for them, they lack an efficient public transportation system, and Amazon seems to have "frozen out" cities without one. That's according to an analysis by Jason Horwitz, director, public policy & economic analysis at Anderson Economic Group. Horwitz correctly predicted nine of the cities on the short list.

If that's true, then good for Amazon. Decent public transportation can make a huge difference to the quality of life in any city. Efficient public transportation, especially if there's a light rail system, gives people an alternative to driving, which cuts down on both traffic slowdowns and air pollution. Public transportation is generally safer than driving yourself. It can save employees thousands of dollars a year, especially if it allows families to forego owning a second car. Because using public transit generally involves some walking, it makes them healthier as well. It allows those who are too old, too young, or otherwise unable to drive to get around on their own. And it's good financial news for the city, generating revenues for decades to come.

You can see why a robust public transportation system might be high on Amazon's wish list. Seattle's public transportation, and all its infrastructure, has been strained by rapid population growth as the city reportedly adds 1,000 new residents every week. Not all of those new residents are headed to jobs at Amazon, but many of them are. As a result, Amazon has been accused of causing, or at least contributing to, Seattle's worsening traffic problem.

It seems highly likely that Amazon CEO Jeff Bezos wants to avoid that sort of controversy at HQ2. One obvious solution (which Amazon appears to be considering) is to locate its new headquarters in the suburbs, rather than right downtown. Google, Apple, and many other high-tech companies have chosen to build massive, self-contained campuses well away from population centers. But that approach has its drawbacks when it comes to recruitment, since most potential employees prefer to step outside into a vibrant urban community rather than a company-controlled campus.

A better place to live.

Besides, cities with a well-functioning transit system simply are better places to live than cities without one. I grew up in New York City, which has extremely efficient transit and I've lived in Paris, where it's even better. Then, a few years ago, I moved to the Seattle area, where there is some public transportation, but it's rudimentary by comparison.

Getting into and around Seattle is a chore that always requires a car. The nearest light rail station is nearly 30 miles away. Buses are an option, but they get caught in traffic too, and it takes an impossibly long time to get from one place to another. 

Even worse is the importance that traffic comes to occupy in one's mind. New York City has terrible traffic as well, but you are almost never stuck driving in it. No matter where you are going, there is always an alternative that allows you to skip the traffic, usually by going under it on the subway or light rail system. 

In Seattle, traffic is a dispiriting fact of life that people plan their days around. I have an acquaintance who can never attend any evening event or social gathering because he has to leave the house at 4 a.m. every day to get to his extremely early work shift. He selected that shift because his only other choice was to spend hours of each day sitting in traffic.

I've many times cut my afternoon errands short for similar reasons--so that I could make it home before the traffic got too bad. Most of the time, I can avoid the worst of it since I work at home. I can't imagine what life is like for the hundreds of thousands who have to commute in it every day from the suburbs to downtown and back again. Most of them have little choice, since home prices and rentals are climbing rapidly in Seattle, and that it's harder and harder to afford to live there.

So kudos to Amazon for making public transit a priority in its search for a new hometown. And if some cities improve their transit systems in a bid for HQ2, all the better. They may or may not wind up with an Amazon campus. But they'll have made their cities much pleasanter places to be.