THE ‘TERRIBLE TROLLEY’ WAS PART OF THE CITY’S STREETCAR LINE UNTIL 1998. PHOTO COURTESY PA TROLLEY MUSEUM

It must be spring migration: The streetcars have returned to Allentown.

Actually, it’s construction. (Which does ramp up in the spring.) Due to a project to replace rails and wires inside the Mount Washington light-rail tunnel, the Blue and Red lines of the T have been rerouted over the hill, running through Allentown then back down winding Arlington Avenue. In so doing, the mid-lane rails that typically only serve to invoke skidding on particularly frosty days are once again serving their intended purpose.

While watching the streetcars descend the mountainside, one of those overly simplistic thoughts occurred to me: Why aren’t these things everywhere?

They were once much more prevalent, of course; at one point, Pittsburgh had the third-largest fleet of streetcars in North America. Many of those lines were discontinued amid additional bridge and highway construction in the middle of the 20th century, as commuter habits shifted (for the worse, many say) toward individual car usage.

I’m certainly not an expert on transportation and infrastructure, as has been repeatedly pointed out to me on social media. But in watching the T glide down Arlington Avenue, I’m pretty sure we’re missing out on something Pittsburgh is uniquely in need of.

It’s no secret that our existing light-rail system is a disappointment, currently of particular relevance only to those living in the southern suburbs (or en route to a Steelers game). The feasibility of extending the T, in one form or another, to Oakland has been considered since 1993.

Thirty-two years is an awful lot of time spent considering. Even by the slow standards of infrastructure development in the modern United States, it seems like we could’ve at least made a decision of some kind in three decades.

Some of that unending hesitation reflects the high cost of subway construction; the 1.2 mile North Shore Connector cost more than $500 million before it opened in 2012. Subways are expensive and difficult to build, particularly in a city defined mainly by rivers and mountains. Light rail lines — particularly “at-grade” lines, which mostly occupy dedicated rights-of-way (but can pass onto the street, as they do in Allentown) — are cheaper.

They also move more people than buses and are more environmentally friendly.

Pittsburgh needs extensive improvements in public transportation, including bus service and other changes to existing systems. Such improvements require funding, which is always a difficult (though not insurmountable) hurdle. But where expansions to the T and wide-ranging light rail service had been promised for decades, serious consideration of such problems has gone mostly silent in recent years.

That’s a shame. It’s an effort that would improve neighborhoods, make the city more accessible and connect more people to civic life — for less than the available alternatives.

I’m sure there are many difficulties that I, a frequently admitted layman, can’t see. But tomorrow, a streetcar will run through my neighborhood and take people into Downtown. There’s no reason why that should only happen because of a detour.