Milepost 0.0

MP 1 on the Mainline, just east of Hunterspoint Avenue
(Photo credit: Dave Keller/Trains Are Fun.com)

In railroad terminology, a "milepost" is literally a post or piece of wood or metal or something placed every mile down a railroad right-of-way.  It's the way everything on the railroad is in reference to.  Every station, siding, yard, switch, interlocking, etc. has a specific milepost where it's located.

The first milepost is placed at "chaining 0"
and then there is [usually] a mile post every 5,280 feet.

Montauk Branch MP 26, as seen from the Wantagh
station platform (Photo credit: The LIRR Today)

One of the most important parts about the milepost system is what spot you choose to be "chaining 0," or basically where MP 0.0 is going to go.  From there you plop one milepost down per mile until you get to the end of the line.

And the railroad's "chaining 0" are pretty interesting.  Usually, mileposts are marked from the city-out.  So on the LIRR "chaining 0" will be on the west side of the island and the mileposts are numbered going east.  On the opposite hand, NJTransit has their mileposts measured going west, since their flipped being on the other side of Manhattan.

MP 104 on the Montauk Branch near AG Siding
in Amagansett (Photo credit: Trains Are Fun.com)

Now if I randomly went up to someone on the train this morning and asked them "Hey! Where's the LIRR's 'chaining 0'?"  If they knew that mileposts are numbered from west to east, the most logical choice would be Penn Station, since pretty much every train goes there.

But they would be incorrect.  The LIRR actually has three different "chaining 0"'s.  The three different MP 0.0's are located at Long Island City, Atlantic Terminal, and Valley Stream.  All of the LIRR's branches measure their mileposts in relation to their distance from one of these three places.

However, if you read the "LIRR's 11 Branches" post and you know that the Port Jefferson Branch starts at Hicksville and doesn't really exist west of there, you might think Hicksville would be a "chaining 0" for the Port Jefferson Branch.  But that's not correct either.  For most of the LIRR's branches, their mileposts are just continued from the line from which they split.

Mineola is technically at MP 18.5.  The Oyster Bay Branch splits off just east of Mineola.  Does that make East Williston at MP 1.3 since it's 1.3 miles up the Oyster Bay Branch?  Since Mineola is not one of the three "chaining 0"'s on the railroad, the mileposts on the Oyster Bay Branch are just continued off the mainline.  So East Williston is really at milepost 19.8.

The same thing works with the Port Washington, Port Jefferson, Hempstead and Central branches.  Their mileposts are just continued off the Mainline.  All of these branches (including the Oyster Bay branch as used in the example above) have their mileposts measured from Long Island City.

It works slightly differently for the Far Rockaway, Long Beach, and West Hempstead Branches.  Like we said in yesterday's VALLEY Interlocking Walkthrough, these three branches officially begin at Valley Stream.  But since Valley Stream is one of the three "chaining 0"'s on the railroad, these branches have their mileposts measured from Valley Stream, not Long Island City or Brooklyn.

The Atlantic Branch, which originates at Brooklyn and not Long Island City, instead has its mileposts measured from there.

So to tie this all together, here's a table with all of the branches, where all their mileposts are measured from, and what the easternmost milepost on the branch is:

Branch	“Chaining 0”	Easternmost Point
Mainline	Long Island City (via Main)	Greenport Yard (MP 94.3)
Montauk Branch	Long Island City (via Mtk)	Montauk Yard (MP 115.8)
Atlantic Branch	Atlantic Terminal	Valley Stream (MP 15.8)
Port Washington Branch	Long Island City (via Main)	Port Washington (MP 18.1)
Hempstead Branch	Long Island City (via Main)	Hempstead (MP 19.8)
Oyster Bay Branch	Long Island City (via Main)	Oyster Bay Yard (MP 33.2)
Port Jefferson Branch	Long Island City (via Main)	Port Jefferson E. Yd (MP 58.2)
Central Branch	Long Island City (via Main)	BABYLON Int. (MP 35.8)
Far Rockaway Branch	Valley Stream	Far Rockaway (MP 5.0)
Long Beach Branch	Valley Stream	Long Beach (MP 6.9)
West Hempstead Branch	Valley Stream	West Hempstead (MP 4.6)

Comparing Mileposts is an excellent way to compare the location of different places on the railroad.  Even though Mileposts are measured from three different points on the railroad, they are all more or less the same when everything shakes out.  Even though there are two different routes to get from Long Island City (via the Mainline or via the Lower Montauk), two different ways to get from Jamaica to Valley Stream (via the Atlantic Branch or the Montauk Branch), and two different ways to get from Jamaica to Babylon (via the Montauk Branch or the Mainline/Central Branch) everything is pretty much the same.

There may be different physical characteristics that make traveling over one route faster than the other, but from a distance point of view, there is a lot of equality on the railroad.  Take a look at the following diagrams I whipped up quickly in Photoshop (I was trying to draw the lines for the text while on the train, so they might be a bit sloppy, so forgive me) that show the distances between two points via different routings:

MP 31 on the Central Branch.
(Photo credit: Trains Are Fun.com)

It's pretty interesting that there is really no difference distance-wise between two different routings.  Now like I said just before, there are different physical characteristics that might make one routing more desirable than another.  Speed limits and speed restrictions are good examples.  The LIRR Today's cool Speed Limit Map can give you a good overview at speed limits and restrictions.  The more straight green the faster the run.

Like in the instances above, the Mainline would be faster between Long Island City and Jamaica because the Lower Montauk (which isn't really LIRR territory anymore) has a much lower speed limit.  In a similar way, the Atlantic Branch is slightly faster between Jamaica and Valley Stream.  Not only is it 0.4 miles shorter, ducking right out of HALL interlocking is much quicker than the crawl that trains destined for the Montauk Branch usually have to take east of Jamaica.  But between Jamaica and Babylon the Montauk Branch wins out.  Not only is the Mainline/Central combination 0.8 miles longer, the Montauk Branch has a MAS of 80 m.p.h. for huge chunks of the run.  The Mainline has a 40 m.p.h. hangup at DIVIDE interlocking and the Central Branch's MAS is a lower 65 m.p.h.

But in most cases, if a train is routed via a different routing than the scheduled one, the distances and conditions are not all that different, so the schedule wouldn't really be impacted.  In each case one option is faster than the other, but only by a couple minutes in most cases when push comes to shove.

In conclusion, Mileposts are interesting things.  They serve a very useful purpose as they give a meaningful location to everything on the railroad.  It's a very simple system that dates back to the dawn of railroading.  No complex GPS systems or satellite receivers giving latitude and longitude coordinates that nobody understands, just chunks of painted wood shoved in the ground.  Couldn't be much simpler.

For more photos of different LIRR mileposts, check out Steve Lynch's Trains Are Fun.com page on LIRR Mileposts.