As mentioned above, three of the original tunnels on the Pennsylvania Turnpike have been bypassed. As originally built (or, rather, converted from old railroad tunnels), the tunnels only carried two lanes of traffic, which meant drivers had to merge at the entrance to every tunnel. As traffic volumes increased on the turnpike, these bottlenecks caused frequent traffic jams.
The situation at Laurel Hill was the first one dealt with; the tunnel was bypassed in 1964. A new 2-lane tunnel was built at Allegheny Mountain adjacent to the existing tunnel, and the new tunnel opened in 1965, with the original tunnel reopening in 1966, after a renovation, finally allowing four lanes of traffic through.
The Kittatinny, Blue Mountain, and Tuscarora Mountain tunnels were also twinned, with the new tubes opening in 1968 and the original tunnels reopening, after their renovations, between 1970 and 1971.
The Ray’s Hill and Sideling Hill tunnels were bypassed by a new 13.5-mile alignment, which opened in 1968. The new alignment also bypassed a service plaza that had been just east of the Sideling Hill tunnel, replacing it with a new plaza that served both directions of traffic, unlike the existing service plazas, which stood at various locations on either side of the road serving traffic in one direction only.
Finally, the Lehigh tunnel on the Northeast Extension was twinned in the early 1990s.
The bypassed tunnels are still very much in existence, although reaching any of them requires a little bit of a trek through the wilds of Pennsylvania. The easiest point to reach is the west portal of the Sideling Hill tunnel. Here’s how:
Exit the turnpike at Breezewood (exit 161, formerly exit 12). Most of the long exit ramp is actually the old alignment of the turnpike that led to and through the Sideling Hill and Ray’s Hill tunnels, but that alignment is blocked off at a point shortly before the exit ramp ends at U.S. 30. Turn right (eastbound) onto U.S. 30, the opposite direction from the connection to Interstate 70.
Drive several miles, first crossing under an old overpass carrying the old alignment and then crossing over the current alignment. Watch for an intersection with Pennsylvania state highway 915 to the south. Northbound 915 becomes multiplexed with U.S. 30 here, but after less than a mile, it leaves U.S. 30 to head north again. Make the left turn onto northbound 915.
(When coming from the south on westbound Interstate 70, it’s possible to bypass the Breezewood mess by using exit 151, formerly exit 30, which is highway 915.)
915 winds through the woods, again crossing the current turnpike at one point, and after about three miles, there is a sharp right turn and the first noticeable downhill grade. (At this point, you have already driven on top of the Sideling Hill tunnel on 915, and the current turnpike alignment also passes over the tunnel.) On the left here, there is a trailhead marked with a “Tunnel Trail” sign. The steep trail runs down towards the tunnel and is about three-quarters of a mile long.
There is an easier route involving less walking than the Tunnel Trail route. Stay in the car and, about 100 yards from the Tunnel Trail trailhead, make a sharp left onto Oregon Road, which is a winding, narrow gravel road.
After about a mile, there is a ranger station on the left side of the road, a log cabin with a small parking area next to it. Park here. Behind the ranger station, past a gate to keep vehicles off of it, a wide path runs for about 150 yards through a clearing and then briefly through the woods before going up an embankment to meet the former turnpike right of way just west of the Sideling Hill tunnel.
Of course, there are no old signs still standing along the old turnpike, and most of the paint visible on the roadway is actually the result of latter-day paint testing by the Turnpike Commission, but the concrete pavement still looks fairly good despite not having been maintained in 30 years. It’s easy to imagine the ghosts of traffic past on the old Turnpike, the Chevy Bel Airs and the Ford Falcons leaving the tunnel and accelerating to 70 miles per hour in one direction, while the horns honk and tempers flare in the other direction as two lanes of traffic funnel into one. And it’s easy to imagine yourself as the sole survivor of some nightmarish Apocalypse scenario that, if nothing else, gave you the ability to lie down in the middle of an Interstate and gaze up at the clouds.
From here, it’s possible to hike the old road for a couple of miles west, towards the Ray’s Hill tunnel. The Sideling Hill tunnel is posted “no trespassing,” has no lights, and is well over a mile long, so enter at your own risk. This is state forest land, so it’s public property, and depending on the season, you may encounter people on all-terrain vehicles, snowmobiles, or cross-country skis. At certain times of the year, you may also encounter people with shotguns, so watch out if you’re not wearing bright colors.
It’s even easier to do this as a virtual trip, albeit slightly less satisfying, by using Terraserver with a starting location of Breezewood, and then following the old alignment northeast (as noted above, it starts off as an exit ramp from the current alignment). The Ray’s Hill tunnel is fairly close to Breezewood, and then the Sideling Hill tunnel is beyond that.