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Interchange Index
Overview: I-276, the Pennsylvania Turnpike (Delaware River Extension), runs east-west through this photo. I-476 runs from the southwest corner to the northeast, and leaves northward; this is known as the Mid-County Expressway south of I-276, and the Pennsylvania Turnpike Northern Extension north of I-276. The major local road running north-south here is the Germantown Pike. Another local roadway, which plays a small part in this junction, is Plymouth Road; this runs WNW/ESE through the middle of the photo, and crosses I-276 just east of the Germantown Pike overpass.
Germantown Pike is Exit 333 (the "Norristown Interchange") on I-276 and Exit 20 from I-476. I-476 South is Exit 334 from I-276 westbound. Being that the Northeast Extension is part of the same toll ticket system as I-276, the 276/476 North junction has no exit number from either highway; it's known as the Mid-County interchange on the Pennsylvania Turnpike.
Interchange Description: Starting from the west, we have the Norristown Interchange on the Pennsylvania Turnpike. Exit 333 itself is a simple trumpet interchange, which probably has been in that configuration since the Turnpike was first built. After exiting, motorists reach a toll booth; on the other side of the toll booth, the connections to Germantown Pike and Plymouth Road are a little more interesting. The connector road runs straight through to Plymouth Road, with an offramp to Germantown Pike southbound and one to I-476, and two onramps to give both directions of Germantown Pike access to the Turnpike. Traffic from the Turnpike bound for Germantown Pike northbound must take a left at the end of this connector onto Plymouth Road, and then travel back west across the Turnpike to Germantown Pike.
Just south of (and partially overlapping with) the Norristown Interchange is Exit 20 on I-476. This is basically a quarter-cloverleaf at Germantown Pike and a half-diamond at Plymouth Road. Access at Germantown Pike is only avaiable between I-476 to the south and Germantown Pike to the north. (The ramp from Germantown Pike SB to I-476 has an interesting bridge under the ramp from I-276 to Germantown Pike SB, to avoid weaving and allow both of these ramps to have wider radii.) I-476 NB traffic bound for Germantown Pike SB uses Exit 19 and Chemical Road, both of which are south of this aerial view; traffic coming to and from the Northeast Extension can take I-276 west to Exit 333, and exit there directly to Germantown Pike. Interesting to note about this part of the interchange is the configuration of the ramps; both the Germantown Pike and Plymouth Road junctions are accessible by collector-distributor roads, which split from I-476 south of the toll booths and run around either side of the large Mid-County toll plaza. Thus, traffic going from the free section of I-476 to local roads doesn't pay the toll for the Northeast Extension of the Turnpike. Access is also available from these collector-distributor roads to I-276; I-476 traffic uses the Germantown Pike North exit, goes under I-476 and the I-276 connector, and then uses a second loop ramp to get onto the Turnpike. I-276 to I-476 traffic has a direct connection, just east of Germantown Pike. (Note that these movements are not incredibly important, as I-476 NB to I-276 WB and I-276 EB to I-476 SB traffic can use I-76 for a more direct and shorter connection, and traffic to and from the east has direct ramps at the I-276/I-476 crossover.
Six more ramps provide connections at the point where I-276 and I-476 actually cross. Four ramps handle traffic coming to and from the Northeast Extension; these form a simple half-cloverleaf pointing to the north. The other two provide access between the south and west; I-476 NB to I-276 EB is a simple right-turn sliip ramp, and I-276 WB to I-476 SB is a nicely built exit from I-276 which merges into the left side of the Blue Route. Note that these two connections, as well as the I-476 through traffic between the Blue Route and the Northeast Extension, must pay a toll at the larger Mid-County toll plaza near Germantown Pike.
Comments: I really have no gripes about this interchange. It seems to be pretty well-built, with direct connections for everything important. The one thing that I might change would be to add a ramp from I-276 directly to Germantown Pike northbound, to get this traffic off of Plymouth Road. There's really only one place where this ramp would fit, which would be right along the inside of the ramp that turns traffic from the I-276 connector back around to I-476 southbound. A simple loop ramp might fit here, but its radius would be tight, forcing traffic to slow down quite a bit and possibly interfere with I-276 to I-476 traffic. This would also create a less-than-ideal weaving situation under the I-276 connector on Germantown Pike, where traffic from this new ramp would have to dodge traffic from the Pike NB headed for the I-276 ramp. If Plymouth Road were more developed, or if congestion on it were more of a problem, I'd say this might be necessary; right now, though, it might be more trouble than it's worth.
History: The image on the right shows the original configuration of this junction, from a Terraserver/USGS topo map dating from July 1983. At the time, I-476 didn't exist; the Mid-County Expressway was still just a blue line on a planning map, and the Northeast Extension was numbered PA 9. The interchange was quite simple; between the Turnpike and Germantown Pike, there was a double-trumpet interchange with a ticketed toll booth on the connecting road. The junction at the beginning of the Northeast Extension was also a simple trumpet interchange; the loop ramps were located where the southeastern part of the 276/476 junction now stands. There was no toll collected or ticket distributed here, as PA 9 is on the same ticket system as the rest of the turnpike. Another note is that, at the time, Pennsylvania was still using sequential exit numbering rather than the newer milepost-based system, so the Germantown Pike/Norristown exit was Exit 25 and the Northeast Extension was Exit 25A. Also note the different alignment of the Plymouth Road overpass over I-276; instead of the little dogleg it has now, which gives it a more perendicular crossing with I-276 and a right-angle intersection at Germantown Pike, it used to run in a perfectly straight line. This old alignment created a longer bridge over I-276 and a bad angular intersection with Germantown Pike, which is probably why it was reconstructed in its current state.
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