Enhancing Safety and Operations at Complex Interchanges With Improved Signing, Markings, and Integrated Geometry

Appendix A. Candidate Site Information Sheets (Supplement to Chapter 4)

Introduction

This appendix provides information on 13 candidate locations for data collection in this project. Each page shows which of the attributes of interchange complexity are present at the location (i.e., written in black lettering), and which were not (i.e., written in gray lettering). In addition, an aerial view as well as a brief narrative describing each location is provided.

Location 1: I-880 at SR 237 in Milpitas, CA

Shown in figure 85, this interchange comprises a major direction change for a corridor of high-occupancy vehicle and tolling (HO/T) lanes developed by the Santa Clara Valley Transportation Authority. The function of this corridor is to serve a major movement between I-880 and the SR 237 freeway.

©Esri.

Figure 85. Photo. Aerial view of location 1.⁽⁵³⁾

One key feature of this interchange is the movement from SR 237 to I-880 northbound. Both the HO/T and general-purpose lanes occupy the same carriageway until a split within the interchange, essentially allowing for all northbound movements to serve as one continuous roadway with what appears to be an HO/T bypass lane.

Location 2: I-110 at I-105 in Los Angeles, CA

Shown in figure 86, this interchange is a modified four-level interchange with one loop ramp and direct HO/T connections from I-105 to the north side of the interchange. There are no HO/T direct connections from I-105 to I-110 southbound or from I-110 northbound to I-105.

©Esri.

Figure 86. Photo. Aerial view of location 2.⁽⁵⁴⁾

All approaches feature some combination of option lanes, auxiliary lanes, and access to service interchanges within the interchange influence area. Notable also is that the HO/T exits are not out of sequence on southbound I-110, as the first exit is for westbound I-105 and the second exit is for eastbound I-105, consistent with right-hand and left-hand conventions.

Location 3: I-5 at California Routes 22 and 57 Freeways in Santa Ana, CA

Shown in figure 87, this interchange is a five-way junction with access to numerous heavily traveled arterial routes from the 22 Freeway. In general, exits conform to the first exit for right-hand movements sequencing method, with the exception of the 57 Freeway connection to I-5, which is also served by heavy-occupancy vehicle direct-connection ramps for movements in the same cardinal direction only.

©Esri.

Figure 87. Photo. Aerial view of location 3.⁽⁵⁵⁾

This interchange features a redundant bypass lane for southbound I-5 traffic, intended for vehicles bound for the service interchange to the south. There is also a slip ramp from the entrance ramp from the 22 Freeway serving this short C/D roadway.

Location 4: I-75 at I-285 Northwest Junction in Atlanta, GA

Shown in figure 88, the interchange is a modified cloverleaf interchange with direct-connection ramps for the primary movements. In its present configuration, the interchange features several braided connections to adjacent service interchanges, and access is provided to and from interchanges from all directions of all freeways, an unusual approach. The interchange is a modification of the original interchange, which featured left exits from the I-285 mainline, similar to the interchange of I-285 and I-20 east of Atlanta. It is slated for modifications related to the I-75/575 HO/T lane program, expected to include direct-connection ramps from the outside lanes of I-285 to the inside lanes of I-75.

©Esri.

Figure 88. Photo. Aerial view of location 4.⁽⁵⁶⁾

Location 5: I-75 at I-85 North Junction in Atlanta, GA

Shown in figure 89 this interchange is the major split of I-75 and I-85 north of downtown Atlanta. Interestingly, despite that I-85 traffic is headed northwest and I-75 traffic is headed northeast, the interchange places the movements in the left and right lanes, respectively. Recently, this interchange, which does not include option lanes, received new guide signing—APL. Previous approaches to signing in this interchange have included angled down arrows, clearly indicating major movement curvature and direction. The interchange also uses non-colored pavement markings for the major movement route numbers.

©Esri.

Figure 89. Photo. Aerial view of location 5.⁽⁵⁷⁾

Location 6: I-85 at I-285 Southwest Junction in College Park, GA

Shown in figure 90, this interchange provides complete separation of mainline traffic for I-285 and I-85, while facilitating all connections between the two routes, serving three intersecting freeway corridors. The quad-carriageway design, similar to I-88 at I-355 in west suburban Chicago, IL, also provides full access to an embedded service interchange.

©Esri.

Figure 90. Photo. Aerial view of location 6.⁽⁵⁸⁾

The interchange uses a somewhat conventional loop-ramp design, similar to the eastern end of Study Interchange 10, to serve movements outside of the I-85 mainline and I-285 route continuity movements.

Location 7: I-85 at Georgia Route 400 Toll Road in Atlanta, GA

Shown in figure 91, this interchange features a type of C/D roadway in the form of a parallel multilane facility, Georgia SR 13, with this collector being largely inaccessible from I-85. The guide signing in this interchange has been recently replaced with APL signing. The northbound lanes feature a four-lane to three-lane/two-lane split, and gore area markings indicate pavement marking changes from a previous configuration. Two heavy-occupancy vehicle-only ramps serve a local facility within the interchange area, with access to and from the northeast only. This segment of I-85 features HO/T lanes.

©Esri.

Figure 91. Photo. Aerial view of location 7.⁽⁵⁹⁾

Location 8: I-85 at I-285 Northeast Junction in Atlanta, GA

Shown in figure 92, this interchange typifies four-level interchange design with high-volume connections between the intersecting freeways, including option lanes on the mainline access to the ramps and on the ramps at the splits for the two directions of I-285.

©Esri.

Figure 92. Photo. Aerial view of location 8.⁽⁶⁰⁾

Location 9: I-35W at Minnesota Crosstown Freeway/TH 62 in Minneapolis, MN

Shown in figure 93, this interchange did not employ C/D roadways in its previous configuration. The present interchange fully separates through movements for both intersecting routes. Most notable in this interchange is the consistent use of dotted lane line markings (drop line markings, which, in Minnesota, are distinguished as a 3-ft line with a 12-ft space), particularly on the ramps serving southbound I-35W traffic to both TH 62 and adjacent local streets. Despite its extremely constrained size, the interchange sacrifices little in the way of readily discernible geometry.

©Esri.

Figure 93. Photo. Aerial view of location 9.⁽⁶¹⁾

Location 10: I-35W at Highways 36 and 280 in Minneapolis, MN

Shown in figure 94, this interchange provides access to Highway 280 from I-35W southbound in two locations because of the unseparated entrance lane from westbound Highway 36 to southbound I-35W. A similar braided geometry occurs in the northbound direction, effectively providing two carriageways for I-35W northbound through traffic.

In the southbound direction, I-35W is signed for an advisory speed of 50 mi/h using inset panels on the primary guide signing.

©Esri.

Figure 94. Photo. Aerial view of location 10.⁽⁶²⁾

Location 11: I-394 at Highway 100 in Golden Valley, MN

Shown in figure 95, this interchange serves the I-394 HO/T lanes barrier-separated section with ramps to and from downtown Minneapolis. The interchange features two direct-access ramps, serving both northbound and southbound directions of Highway 100 and, in the westbound direction of I-394, access to a local roadway.

West of this location, the HO/T lanes become congruent with the general-purpose lanes, as opposed to the barrier-separated reversible facility that exists to the east of here.

©Esri.

Figure 95. Photo. Aerial view of location 11.⁽⁶³⁾

Location 12: I-5 at I-90 and Seattle Downtown Exits in Seattle, WA

Shown in figure 96, this interchange is of mid-1960s vintage, with I-90 access in the southbound direction being moved. Improvements here are planned and include northbound freeway-to-freeway ramp metering, a reconfiguration of the northbound mainline lanes to permit two entering lanes from the C/D roadway, and other changes to local access. Adding to the complexity is the entrance to the express lanes facility, which is not restricted access. During the morning peak period, this entrance is closed, and the left lane through traffic must merge into a mandatory movement for a left exit to a service interchange.

©Esri.

Figure 96. Photo. Aerial view of location 12.⁽⁶⁴⁾

Location 13: I-5 at I-405 and Route 518 in Tukwila, WA

Shown in figure 97, this junction is characterized by three distinct treatments of the upstream exit to a service interchange with downstream exit only (including option lane) within the system interchange. While the guide signing uses the type A, type B, and down arrow methodology, signing of option lanes is inconsistent within the interchange, and issues with sign structure maintenance have resulted in the elimination of signing and downsizing of some signs, particularly those closer to the decision points. A southbound left exit for a major movement is a compound exit, with a heavy-occupancy vehicle lane adjacent to the general-purpose exiting lane.

©Esri.

Figure 97. Photo. Aerial view of location 13.⁽⁶⁵⁾