A Brief Introduction to the
Newhall Pass (SR-14) and Weldon Summit (I-5) form two arms of a very important passageway through the mountain barrier north of Los Angeles. This pass helps connect Southern California with the rest of the state. It is one of the few passages through that barrier as well. As a result, traffic volumes are quite high, particularly commercial traffic. Commercial traffic has been a “problem” since the 1860’s when heavy amounts of wagons passed through here on their way to the gold fields of Kern County. The traffic was so heavy back then that it became one of the first paved roadways in California as oil from the nearby hills was used to reduce dust and erosion on the road. Traffic has only increased since then. The pass is also rather steep, even today. Grades approaching 6% still exist on both sides of the pass on the current freeways. Why this is a problem and how the California Division of Highways (later Caltrans) works to solve this problem will be discussed.
Map of the interchange
Original Interchange – US 6 and US 99
In 1955, the first section of the Golden State Freeway was completed through here. The new freeway ran from near Sepulveda Junction (State 7) to near Tunnel Station Junction (US 6). It helped to reduce the traffic problems at Tunnel Station Junction through the construction of direct connectors. Ramps were built to connect US 6 West with US 99 South and US 99 North to US 6 East. The resultant interchange, a three level interchange, remained in use until about 1973 when the new interchange for I-5 and State 14 was opened to traffic.
Early Plans, the Reseda Freeway,
and the “Full Interchange”
As traffic counts grew in the pass, it was determined that another upgrade to the interchange was needed. With the considerable commercial traffic in addition to the importance of the pass, a plan was proposed to create a sort of “dual freeway” through here. A new freeway alignment, to the west, would be constructed for auto traffic. The existing freeway would be converted to a “truck freeway”. This new arrangement would allow for slower trucks to climb the grade easier and interfere less with the auto traffic. The truck freeway would also have most of the connections that the mainline freeway had to help reduce the need for merging problems with the commercial traffic.
The main interchange between I-5 and SR-14, as it was originally designed, would allow for the future extension of SR-14 south of I-5. This extension, known as the Reseda Freeway, would have eventually carried SR-14 through the San Fernando Valley to SR-1 near Temescal Canyon Road. Through the pass area, the Reseda Freeway would have paralleled I-5 from the current SR-14 junction to about Balboa Blvd. From there, the route was never precisely determined.
Initial Construction – 1969 to 1971
Construction on the new interchange began in 1969. This was to be a major project, construction the south end of the Antelope Valley Freeway, the realignment of the Golden State Freeway, and the reconstruction of the former freeway. Massive amounts of grading was needed for this project, far more than any other project through here before. Extensive cuts, some more than 250′ in depth, were required along the new freeway routes. These cuts helped lower the elevation of the summits for both Newhall Pass and Weldon Summit.
As this iteration of the interchange was built with plans for a southern extension of Route 14, certain things were implemented in the design. Signage, as it was originally planned, showed the somewhat unique signage that was to be applied to the full interchange. State 14 South was to have the control point of “Beach Cities”, where State 14 North had “Palmdale”. Putting those two together at a time when there was a popular, albeit incorrect, notion that “California was to fall into the sea”, was rather amusing considering the 14 crosses the San Andreas Fault in Palmdale. Another difference was the addition of a short connector ramp between the SR-14 Southbound Truck Connector and the mainline SR-14 Southbound to I-5 Northbound Connector ramp. This was, in part, to be constructed as a part of the southern Route 14 extension. It was not built but the bridges were built to accommodate it.
February 9, 1971 Earthquake Damage
Construction was nearly complete on the new interchange until the early morning of February 9, 1971. The Sylmar/San Fernando Earthquake, a 6.6 magnitude earthquake, severely damaged the interchange. Some of the tallest columns, forming the supports for the I-5 SB to SR-14 NB connector, collapsed during the quake and crushed a recently constructed crane.
Changes were made to the freeway plans after the earthquake. Signage for State 14 South was eliminated as well as the short connector near the Sierra Highway Undercrossing for I-5 South and SR-14. These changes in the design plans seem to show that, should the Reseda Freeway be built, it wouldn’t be for quite some time. Despite that, the interchange that was finally constructed did leave room for that freeway. Construction, or reconstruction in this case, was finally completed in 1975.
The partially collapsed interchange was also featured on the cover of a 1973 Doobie Brothers album – Captain and Me.
January 17, 1994 Earthquake Damage
Much like in 1971, another major earthquake damaged the interchange again. Unlike the last time, the freeways involved were open to traffic. There were a few deaths at the interchange as a result of the collapsing bridges. The most notable collapse was the SB 14 to SB 5 connector bridge as it passed over the mainline I-5. This was mostly due to a difference in shaking between the taller and shorter columns. A similar collapse occurred on the 14 SB to 5 NB connector as it passed over the SB 14 to SB 5 truck lanes. Shaking in this area was intensified due to the sedimentary basin being rather deep here. The interchange was again rebuilt but this time a bit differently. To help reduce the problem of different column height, the shorter columns were made deeper to create less of a difference in height and to allow the entire structure to resonate at a similar frequency during an earthquake. Only time will tell if this new idea will work out.
Starting in 2008, construction began to add a new HOV connector ramp between I-5 and SR-14. The addition of this new ramp posed a few problems, mostly dealing with the limited space for adding additional lanes or bridges. To make this task a bit easier, Caltrans decided to move the San Fernando Road exit on I-5 a bit further north. Doing so eliminated the need for a short overcrossing from I-5 SB over the SB 14 connector lanes. The new SB I-5 San Fernando Road exit now runs alongside the west/south side of the interchange. The new ramps were completed in 2012.
Existing evidence of the Full Interchange
While most of the evidence for the “Full Interchange” was erased when the interchange was rebuilt in 1994, there are a few key features remaining. Stub ramps, such as the I-5 SB to SR-14 (Reseda Freeway) and the truck connector from SR-14 SB to I-5 NB are still visible. Other stub ramps, such as the SB 14 to SB 14 connector have been too heavily modified by later reconstruction.
The above photo shows the ramp stubs along I-5. Two are visible here. The first at location A, the SB 5 to SB 14 ramp, is seen near where the SB 5 truck ramp tunnel begins in the upper third of the image. The second, at location B, the NB 14 to NB 5 ramp, is seen as a cleaner or brighter section of concrete on the right side of the mainline freeway, in the bottom third of the image.
Along State 14, three ramp stubs can be seen. The first, at location A, is the former SB 14 Truck to SB 14/NB 5 connection. Asphalt and a wider bridge over Sierra Highway are all that remain of this ramp, which was never constructed. The second, at location B, would have been the SB 14 to SB 14 connection. This stub was obliterated in 1994. The last, at location C, would have been the NB 14 to NB 14 connector. Note that all of these ramps would have been one lane, at least where they met the mainline freeway.