City Modeling

One way is to mix up the Woodland Scenics Smooth-it , part of their road system and pour it between the rails, then before it dries run a truck down the rail before it dries and wipe away or scrape away any excess. Walthers is now also offering an asphalt street system, pages 433 or 479 of the 2006 book. 933-3194 and 3195 are the #s.

You can cut pieces of styrene and Goo! them down in place between the rails. You can paint them asphalt color, or whatever texture you want. You can also plaster in these places and then run trucks over them before it dries, which is similar to what the post before me was suggesting.

You can try something the real railroads often do to keep the flangeways clear.  Glue or spike a guardrail just inside both running rails (use a NMRA gauge to make sure the guard rails don't get too close to the running rails), then pour whatever goop you use for paving material in between the guardrails.  You can make a narrow scraper tool out of styrene to level the paving with the top of the guardrails.  Also, it may be wise to use rail slightly shorter than the running rails to make the guard rails, i.e. use code 83 guardrails with code 100 running rails.  This will ensure that the running rails can still be kept clean with an abrasive block or whatever you use.

Tom

Use .040" styrene for the street surfaces.  Cut it to fit the inside/outside of the rail.  You'll need to support the curb with something to avoid having too high of a crown (the slope from the center of the street to the curb).  Raising the street .080" at the curb would give a reasonable crown.

Use 1/16" strips between the rails.  Evergreen 1/16" tile makes a good approximation to the rubber fillers used at real grade crossings.

I have to admit that I've never had a lot of luck constructing grade crossings that looked like, well, grade crossings.  But cbq9911a gives me an idea or two and think I'll give future consideration to his methodology.  Thanks, there, cbq9911a.

If you are modeling concrete roads, I think the thin sheets of styrene is the best method because it is easy to shape it and score expansion joints as well as pavement cracks. Asphalt roads are far more common because most roads are going to get resurfaced from time to time. Plaster or similar product such as WS Smoothit work well but you will probably have to sand it smooth since it is difficult to get wet plaster smoothed out. You might also have to fill in voids before you sand. The key to realistic roads is to get a proper base color and then do a good job of weathering. Both concrete and asphalt tend to bleach out over time but they will accumulate oil and rubber debris over time, darkening the part of the lanes where vehicles travel. Also doing the proper lane markers for your era and locale is important.

Trolleyville's Schoolhouse section has a detailed tutorial + photos on paving track-embedded streets...

Part 1 with Styrene => http://www.trolleyville.com/tv/school/lesson6_3/
Part 2 with Durham Water Putty => http://www.trolleyville.com/tv/school/lesson6_4/

Some of the Part 2 article gives the following instructions about making a screed...

Make a "screed" from .080" styrene to fit between the rails. Notch each corner of the screed about .030" so the top of the paving will be below the rail so it won't be damaged when the rails are cleaned with a Bright Boy abrasive pad. Make another screed from .080 styrene to span the distance from the rail to the curb. Notch it about .030" on the rail end and whatever your curb height will be on the sidewalk end. This screed should have an arc to simulate the crowned road. Test the screeds by dragging them in the areas you're going to pave to be sure that the rails and curbs are smooth.

They also explain their preference for Floquil oil-based paints instead of water-based latex paint.

P.S.: You can get the water putty for a few dollars at any hardware store or building supply.