Arlington is a highly desirable place to live, and I am proud to have represented it for decades as an elected official. I am also proud that my county is moving forward with a new streetcar system.

I started my public service in Arlington on the school board in 1976. At that time, Arlington faced a storm of controversy about a major new transit project: Metrorail. A small but vocal faction of our community claimed that the proposed Orange, Blue and Yellow lines were too expensive and risky and argued that we should just use buses instead. After much deliberation, Arlington invested in rail.

The rest is history.

Investing in Metrorail transformed Arlington and Northern Virginia. Arlington wisely decided to run the Orange Line down the aging Wilson Boulevard corridor, with urban stations underground, rather than in the median of Interstate 66, as the original plan called for. Those Metrorail stations became powerful catalysts for economic development. In fact, investing in rail is widely regarded as the principal factor that propelled Arlington from a community in economic decline in the 1970s to one of the most desirable places in the country to live and work.

I was eventually elected to the Arlington County Board, for which I served as Arlington’s representative on the Washington Metropolitan Area Transit Authority board for a decade. During those years, I learned how bus and rail work in different ways to sustain our economy. Buses have their place, but bus routes are temporary and changeable. As a fixed-rail network, the Arlington streetcar will provide a permanent transportation anchor for investment where it is most needed in the coming years.

But our historical success with rail investment is not the only reason to invest in the streetcar. I have a personal interest in maintaining the rich diversity that makes Arlington a true community. To help preserve Arlington’s diversity — of age, heritage and income level — we must preserve affordable housing. As a small county, however, we have limited space to expand our housing stock. The Columbia Pike corridor represents our best chance to meet this need.

The Columbia Pike neighborhoods plan calls for the preservation of more than 6,000 affordable homes and apartments, all made possible by new development density around planned transit stops in the corridor. Many of these residents will be transit-dependent, while others will have automobiles that will clog the limited street network. Without the streetcar, we simply won’t be able to handle this transportation burden.

Finally there is one additional reason for rail investment in south Arlington: fairness. All of Arlington paid (and continues to pay) for the Orange and Silver line corridor in north Arlington, yet only north Arlingtonians have seen their property values skyrocket as a result. Now south Arlington deserves to have the favor returned.

Fortunately, the Arlington County Board is holding fast to its decision to move forward, and I hope it retains the courage the community had 40 years ago to make this transformational investment.

The writer, a Democrat, retired from the Virginia Senate in 2012.