...pavement is involved over them? In other words lets say we have some tracks, an old trolley line in this case that runs down a street. Let's say the street is all brick. I'm actually using Galveston as an example here. What is the track structure like underneath? Is it standard railroad tie construction which is then buried or is there another special method? I know trolley tracks are a bit different from freight lines so for the sake of comparison let's also pose the same question for freight lines running down the middle of streets. If they are standard ties, how you can monitor the condition of them or know when something is going bad?
Fred
According to Sir Mudchicken, I believe the rules are as follows:
(1) When laying track below asphault, the first step is to change your mind and find a new location;
(2) The second step, should you decide to continue is to see Rule Number One.
I, of course, have no personal knowledge of these rules. But, I Mudchicken pretty much explained it to me in a format that I could understand it.
Gabe
In the case of a brick or cobblestone pavement, the trolly line is put in first and then the bricks or cobblestones are cut to fit around the track. In some areas I believe thin, steel crossties were used.
Street trackage on modern light rail lines is often directly secured to concrete slabs. But the way it was usually done in days past (and the way it is still done on freight railroads in city streets) is to lay a standard track structure under the street (wooden ties and all) and cover it up with pavement. The South Shore in Michigan City and the UP (former SP) line on Embarcadero Street in Oakland are both constructed in this manner. You are, of course, correct, that you can't directly see the ties with this sort of construction. But you can determine whether the ties are doing their job from other indicia. For example, if the track isn't holding gauge or surface, you could very well have a tie problem, It's not conceptually different than a grade crossing, where the pavement crosses over standard railroad track.
One additional (but not well known) difference between streetcar tracks and standard RR tracks. Many streetcar lines had track designed for so-called "tram" wheels rather than standard railroad wheels. A tram wheel had a narrower and shallower flange than a standard wheel and also a narrower tread (so the wheel wouldn't overhang the rail head and hit the pavement). The narrower flange meant that the back to back spacing of tram wheel sets was wider than standard wheels on the same gauge.
The upshot was that even a standard gauge streetcar line, if it were designed for tram wheels (and many were), couldn't handle standard railroad equipment. If the guard rails at the switches and crossings were set for the tram wheels, there wouldn't be enough room for the standard flanges to get through, If, on the other hand, the guard rails were set for standard wheels, they wouldn't pull the tram wheelsets over far enough to prevent the wheels from picking frogs. Also, where girder rail was used, girder rail designed for tram wheels could have flangeways so shallow that standard wheels would ride on their flanges rather than on their treads.
This has actually been an issue at some railway museums. The Illinois Railway Museum, for example, has a number of Chicago streetcars which are regularly used. The Chicago system was standard gauge, but was designed for tram wheels. However, at the Museum, the cars must share trackage with cars having standard wheel contours. The solution has been to replace the tram wheels on the operating equipment with standard countour wheels, with associated changes to the brake rigging.
fredswain...pavement is involved over them? In other words lets say we have some tracks, an old trolley line in this case that runs down a street. Let's say the street is all brick. I'm actually using Galveston as an example here. What is the track structure like underneath? Is it standard railroad tie construction which is then buried or is there another special method? I know trolley tracks are a bit different from freight lines so for the sake of comparison let's also pose the same question for freight lines running down the middle of streets. If they are standard ties, how you can monitor the condition of them or know when something is going bad? Fred
The cheap, crummy, way is to built the track just like always, then lay down hot asphalt right over the track. If the idea is to keep the top of rail at the top of street, then the track has to be depressed into a slot in the finish grade of the street. Asphalt overlay is very common in industrial plants, ports, autoramps, lightly used branchlines running side streets, industrial spurs running in streets, and other locations where the vehicle traffic is relatively infrequent and the rail traffic is slow-speed.
The expensive, good way is to use precast concrete crossing panels lag-screwed to wood ties or affixed with several different systems to concrete ties. This is the preferred method in areas of high vehicular or rail traffic, or when someone else is paying for it, and is common in light-rail applications. Most light-rail construction running in city streets for long distances uses some type of direct-fixation track, however, which dispenses with the crosstie.
When streets were paved with brick, the track was laid in a slot excavated into the finish grade (just like with asphalt pavement), then a sand or tar bedding layer placed, then the pavers.
To repair track that is overlaid with asphalt or pavers, it's necessary to tear up the paving and make a big mess of things. In the days prior to the widespread adoption of pressure-treated ties, track and pavement maintenance employed large forces. With pressure-treated ties, even in such a badly drained application, one can get 35-50 years out of the track structure before it is so far gone that it has to be torn up and fixed.
RWM
I attended the Univ of Montana at Missouls back in the mid-60's. The first few years I was there, Higgins Ave downtown was curb-to-curb brick, but it was obvious that there was a steetcar line that ran down the middle many years prior. Due to the lack of rails, I assume they were ripped up and the slot bricked in. During the ensuing years, the wood ties rotted, and guess what? There was a big dip where every tie was, giving the street a washboard effect. In the sidestreets around campus, the rails were still visable and old photos did corroborate an abandoned steetcar line. Eventually Higgins Ave was ripped up and asphalted, with many of the bricks being re-used at the U of M. So, during the "olden times" as we said in high school, wood was used.
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