Unlike most Interstate numbers, which are assigned by AASHTO to fit into a grid, I-99's number was written into Section 332 of the National Highway Designation Act of 1995 by Bud Shuster, then-chair of the U.S. House Committee on Transportation and Infrastructure, the bill's sponsor, and the representative of the district through which the highway runs. The number "99" violates the AASHTO numbering convention associated with Interstate highways. Under this system, the lowest numbers start on the West Coast progressing in order to the highest numbers on the East Coast. Interstate 99 is out of place as it lies east of Interstate 79 but west of Interstate 81. This inconsistency irks many road enthusiasts, and some have expressed their disapproval of this in various forums, proposing alternative designations including I-81, I-83, I-170, I-390, I-576, I-776, I-976, I-980. The Federal Highway Administration addresses this issue in the "Interstate FAQ" on their web site, explaining that the designation can only be changed by an act of Congress.
When construction on I-99 is completed, the southern terminus of the route will be at an interchange with Interstate 68 in Cumberland, Maryland. The northern terminus will be at an interchange with Interstate 86 in Corning, New York.
Bolded cities are officially-designated control cities for signs
The names given to this road include the Bud Shuster Highway and Appalachian Thruway; the latter name continues north with US 220 and US 15.
Within Pennsylvania, the road ran 51.2 miles (82.4 km), all concurrent with U.S. Route 220, from an indirect connection with the Pennsylvania Turnpike (I-70/76) near Bedford north past Altoona to a temporary terminus at U.S. Route 322. Immediate plans will extend it northeast past State College to I-80 near Bellefonte.
This route continues north towards Altoona.
In Tyrone itself, Interstate 99 is a short elevated expressway at Pennsylvania Route 453. This section is notorious for speed traps as many cars heading downhill from Bald Eagle must brake in order to stay within the speed limit.
Until the end of 2007, the highway ended north of Tyrone at the village of Bald Eagle, where traffic was diverted on to U.S. Route 220. On December 22, 2007, after several long construction delays, the section from Bald Eagle to Port Matilda was opened to traffic. Northbound traffic is currently diverted to U.S. Route 322 eastbound, locally known as Skytop Mountain Road, north of Port Matilda at the crest of Bald Eagle Mountain. Southbound traffic can enter the highway one exit further south, from U.S. Route 322 eastbound at Port Matilda. The southbound lanes in the section between these two exits remains closed for the remediation of the acidic rock. Interstate 99 is expected to be completely open between Port Matilda and State Colllege by the end of November 2008. The section between Bald Eagle, PA and Skytop is not signed as Interstate 99 yet, as legislation by congress is required to post the designation.
Corridor O of the Appalachian Development Highway System was assigned in 1965, running from Cumberland, Maryland (Corridor E, now Interstate 68) to Bellefonte, Pennsylvania (Interstate 80) along U.S. Route 220. The portion in Pennsylvania, from Bedford north to Bald Eagle, was upgraded to a freeway in stages from 1970 to 1995.
As the interchange with the Pennsylvania Turnpike near Bedford was built long before the new freeway opened, there is no direct freeway-to-freeway access between the Turnpike (I-70/76) and I-99. Traffic must use U.S. Route 220 Business, the old alignment of US 220 before the freeway.
In 1991, the Intermodal Surface Transportation Efficiency Act (ISTEA) was signed into law. It included a number of High Priority Corridors, one of which - Corridor 9 - ran along US 220 from Bedford to Williamsport, Pennsylvania, and then north on U.S. Route 15 to Corning, New York.
The National Highway Designation Act of 1995 amended ISTEA; among these amendments were that "the portion of the route referred to in subsection (c)(9) [Corridor 9] is designated as Interstate Route I-99." This was the first Interstate number to be written into law rather than assigned by the American Association of State Highway and Transportation Officials (AASHTO). (Interstate 73 and the extension of Interstate 74 had been defined in 1991 by ISTEA as the "I-73/74 North-South Corridor", but not officially added to the Interstate Highway System or assigned those numbers.)
On November 6, 1998, AASHTO approved the I-99 designation from Bedford to Bald Eagle. Since then, the connection through the Nittany Valley between the existing State College bypass on U.S. Route 322 and Interstate 80 has been built (the northernmost piece was widened from a two-lane freeway in 1997). On its completion in 2002, U.S. Route 220 was rerouted via US 322 and the new road, and the old US 220 north of US 322 was designated U.S. Route 220 Alternate.
The road through the Bald Eagle Valley between Bald Eagle and State College is presently under construction, and the interchange with I-80 is not up to Interstate Highway standards. Construction has been delayed since 2004 by complaints from the Pennsylvania Department of Environmental Protection about acidic surface runoff from unearthed pyritic rock leaking into the groundwater and nearby creeks draining to the Bald Eagle Creek. Excavation began in late 2002, and a year later, more than 3 million cubic meters of excavation spoils had been generated, with up to 30% from a 200 meter vein of Ordovician sandstone (including the Bald Eagle Formation) containing iron sulfide, or pyrite. When exposed to air and water, these minerals produced sulfuric acid, contaminating both surface runoff and groundwater.
PennDOT halted construction in March 2004 to give full attention to resolving the environmental problem posed by the massive pyritic rock piles. As of late 2006, the remediation plan had not been finalized. Original plans to truck the contaminated spoils to strip mine pits were blocked by local opposition at the disposal sites, and the plans were abandoned. Current plans call for moving the piles to another point along the I-99 right-of-way.
As defined in Federal law, I-99 is to continue north to Corning, New York. Signs have been placed along the present U.S. Route 220 and U.S. Route 15, much of which are built to Interstate Highway standards, marking the route as the "Future I-99 Corridor".
From Bald Eagle, Pennsylvania to State College, construction has been held up by lawsuits stemming from environmental contamination when crews unearthed large amounts of acidic rock. The lawsuits have since been settled and a remediation plan is in place that calls for moving much of the acidic rock to a containment site about 3 miles (5 km) south of the present disposal site.
In State College, Interstate 99 is already built and open, but not signed. The routing takes the western half of the Nittany Expressway (U.S. Route 322) and goes northward from Penn State's Research Park. U.S. Route 220 was rerouted here as well, as the old routing used to go directly to Milesburg, Pennsylvania. From Benner Pike in State College, Interstate 99 continues along an old "super 2" highway routing of Pennsylvania Route 26 going towards Bellefonte, Pennsylvania. The current plans are to have Interstate 99 end at Interstate 80.
|Bedford||Bedford Township||0.00||1||I-99 continues south as US 220|
|East St. Clair Township||6.65||7|
|King Township||10.13||10||Blue Knob State Park|
|Allegheny Township||28.12||28||To PA 764|
|Snyder Township||51.84||52||– Bald Eagle|
|Centre||Worth Township||61||– Philipsburg, Port Matilda||Current northern terminus of I-99 southbound|
|Huston Township||Temporary exit; current northern terminus of I-99 northbound|