What is an "interurban?"

[Firelock76]

I've usually taken the lazy man's approach and described interurbans as trolley cars on steroids, that is bigger, heavier, and faster, and instead of traveling between neighborhoods travel between towns or even counties.

Works for me.

[54light15]

I've ridden the Belgian coastal tram end-to-end. It's worth doing and I'd say it qualifies as an interurban. 

[CSSHEGEWISCH]

The consensus tends to define an interurban as electrically powered, with direct suspension overhead and trolley pole pickup.  They are built to lower engineering standards than steam railroads with tight curves and lighter rail.  Equipment is shorter and narrower than steam roads, using radial couplers to handle the curves.  Freight service is minimal to non-existent.  Service tends to be frequent with one or two car trains between relatively nearby cities.

[daveklepper]

Based on comments to the excellent report on the Coastal Tramway in Belgium, I think needed is some clarification of what an interurban is.  Most new light rail lines provide transportation between suburbs and city centers.  Interurbans may or may not do that, but they definitely connect centers, which the Coastal Tramway does, more than two or three along its route.

Pittsburgh had interurban lines south to Charleroi-Rosco and Washington.  Cut back to their present length, they are suburb-to-city light-rail lines, not interurbans.   St. Louis's line to Bellville is an interurban because Bellville is an employment and retail center.  As are Milwaukee, South Bend, Michigan City, and Elgin.  If Baltimore's light rail system were extended to Annapolis and/or to Silver Springs (connection with Washington, DC's Metro), then it would be an interurban system, not just light rail.  Boston's system is definitely just light rail, not an interurban system.  And a multi-metropolitan streetcar system cannot be an interurban unless substantial  trackage is off-street.  Two examples in New England were the New York and Stamford (New Rochelle – Stamford) and Boston and Worcester.  The Eastern Massachusetts lines north to Revere, Lynn, and Salem were very marginally interurban north of Revere.  Los Angeles's Blue Line to Long Beach is an interurban and is even mostly on the old Pacific Electric RoW with similar street-running in Long Beach.

 

The Vienna Baden line in Austria is an interesting interurban line.  I rode it in 1960, with prewar wood mu cars, a two-car train.  (Now getting modern low-floor cars.) Now I believe there is a stretch of trolley-subway running in Vienna, but then it was all surface, shared with the local tram line to the city limits, mostly on street, in pavement shared with autos.  Then came the  separate RoW, though forests and farmland, and then street running again in Baden.  The street single-track terminal, with store-like station and ticket office, was close to a mainline RR overpass.  I aimed my Leica at an oncoming train.  From familiarity with some Yiddish, I was able to evesdrop  following conversation, here translated from the German:

 

"Is that stranger a spy?"   "No, he came on the Blue Tram.  Spies come in private cars."