The idea of putting in a streetcar line along Nicollet and Central Avenues in Minneapolis has been promoted so much that it seems like a done deal. Proponents claim that streetcars would lead to economic development along that corridor, and they note the example of Portland, Ore., to support their view.

I am dubious. As a former epidemiologist, I am alert to the "correlation vs. causation" problem. How does one know that building the Portland streetcar line caused the economic development along Pearl Street? Maybe there were other factors that stimulated development there. And perhaps there were unique circumstances in Portland.

The proposed line for Minneapolis would run along routes that are already served by several bus lines. Streetcars would not provide faster travel, and of course building the line would be expensive. Such duplication seems wasteful.

I was surprised to learn that my opinion on this issue is one usually held by conservatives. I am a liberal Democrat, suspicious that the bus line plus streetcar line idea amounts to a two-tier transportation system, one for the poor and one for the middle class.

My own experience with public transportation here and elsewhere makes me wonder why the city doesn't consider the alternative of improving its existing bus service instead of building a new streetcar system.

My husband and I lived in Edina for 25 years until we became empty-nesters and moved to downtown Minneapolis. We were accustomed to using public transportation when we lived in Chicago (the L) and Boston (the T). Now that we live downtown, we use light rail, and that came easily for us. We had rarely used buses in any city, however, and even though we were motivated to take advantage of the regular bus service that serves downtown, it took some time and effort for us to do so.

The primary barrier was education: How do you ride a bus? That may sound like a ridiculous question, but it is the one what kept us from taking our first step onto a bus. How much does it cost? Do you have to have exact change? What if you have to change buses? How do you know where the bus will stop? And so on.

We eventually figured all of this out, learned how to use our new "Go-To" cards, downloaded a few apps to our phones so we could track some of our buses in real time, and started telling our friends how much easier it is, for example, to get to Uptown by bus than by car and teaching them how to do it.

I realize that the Metro Transit website has instructional information, and that on request they will conduct mini-classes for groups of people who want to learn how to use the bus. Such efforts need to be expanded and advertised.

An additional barrier was uncertainty about bus schedules: How do you know when your bus is supposed to arrive and, more important, how do you know when your bus will actually arrive? Dealing with uncertainty about departure and arrival times is difficult for someone accustomed to being behind the wheel.

Instead of building a redundant streetcar system, let's imagine building a state-of-the-art bus system for the 21st century.

Mary Jo Nissen lives in Minneapolis.