PURPOSE:

 

The purpose of this report is to present to the City Council a proposal by the California Department of Transportation (Caltrans) to reconfigure the Burbank Boulevard Interchange with Interstate 5 into a diamond interchange, and to realign the freeway in the vicinity of the interchange as part of the Interstate 5 High Occupancy Vehicle (HOV) Lanes project.  Caltrans is requesting the City submit a letter of support for the proposed interchange modifications so that they may be incorporated into the overall HOV project.

 

BACKGROUND:

 

Caltrans is currently in the design stage of a project to add High Occupancy Vehicle (HOV) lanes on Interstate 5 between Route 134 and Route 118.  The project, funded by the Metropolitan Transportation Authority, is meant to improve mobility along the Interstate 5 corridor and is a critical improvement for maintaining the region�s air quality conformance.  Within the City of Burbank, the proposed project consists of a number of components that improve both freeway performance and local street levels of service.  In addition to the installation of HOV lanes in the freeway median, the project would add a new interchange at Empire Avenue to connect San Fernando Boulevard near Scott Road to Empire Avenue where it currently terminates at Victory Place.  The interchange would provide full access to the Golden State Area, the Burbank Airport, and the Empire Center via a diamond interchange.  The project would also grade separate the railroad grade crossing at Buena Vista Street and San Fernando Boulevard by raising the Metrolink tracks gradually between a point just north of the Burbank Animal Shelter to Buena Vista Street, where they would cross Buena Vista Street approximately 16 feet above grade, and would then gradually return to grade between Buena Vista Street and Hollywood Way.  Finally, the project would close the current San Fernando Boulevard underpass, one-way roadways, and ramp system between Grismer Street and Victory Place (this connection would be replaced with the Empire Avenue Interchange) and would close the northbound Lincoln Street off-ramp (which would also be replaced with the full interchange at Empire Avenue).  Finally, auxiliary freeway weaving lanes would be added between Burbank Boulevard and Empire Avenue, and between Empire Avenue and Buena Vista Street to improve freeway operations.

 

Since the beginning of project design, it was determined by Caltrans that the width of the Burbank Boulevard overpass is insufficient to install HOV lanes between the existing bridge abutments.  Thus, installation of HOV lanes requires that the portion of the Burbank Boulevard Bridge spanning the freeway (not the portion recently widened by the City) be rebuilt to provide additional width for the new HOV lanes.  Because the HOV lanes requires a complete bridge reconstruction, Caltrans and the Federal Highway Administration (FHWA) have been reviewing the current Burbank Boulevard interchange to determine if an opportunity exists to bring the interchange up to contemporary standards.  In particular, FHWA (which has jurisdiction over Interstate 5 because of its classification as a Federal Interstate Highway) would like to eliminate the sub-standard loop ramps and reconfigure the interchange to a more standard diamond configuration.  To accomplish this reconfiguration, the existing northbound offramp loop ramp to westbound Burbank Boulevard, as well as the southbound onramp loop ramp from westbound Burbank Boulevard would be eliminated.  The remaining ramps would be reconstructed into a tighter alignment with the freeway forming a diamond interchange.  Also, the current northbound onramp, currently located north of the Burbank Boulevard interchange and accessed via Walnut Avenue would be relocated within the Burbank Boulevard diamond interchange and would access the freeway where the existing northbound loop ramp is located.  Finally, to improve mainline design speeds and sightlines, Caltrans would straighten the alignment of the freeway itself between Magnolia Boulevard and just north of Burbank Boulevard.  This would be accomplished by moving the freeway centerline westward by approximately 140 feet.

 

The proposed interchange reconfiguration and freeway realignment would affect properties on both sides of Interstate 5 between Magnolia Boulevard and just north of Burbank Boulevard.  Realignment of the freeway centerline and shifting of the southbound offramp and onramp at Burbank Boulevard would require an acquisition of approximately two acres of privately-owned property west of the freeway between Magnolia Boulevard and Burbank Boulevard to Caltrans, and the use of approximately two acres of city property adjacent to the freeway (abandoned Front Street).  On the east side of the freeway, realignment of the freeway centerline as well as elimination of the loop ramps and tighter configuration of the remaining ramps into a diamond interchange would yield a surplus of property of approximately 4.2 acres adjacent to First Street between Magnolia Boulevard and Burbank Boulevard, and 2.4 acres north of Burbank Boulevard.  The locations of required property dedications and property surpluses that would result with reconfiguration of the interchange are shown on Exhibit A.

 

Caltrans estimates that reconfiguration of the interchange and realignment of the freeway could be done for a relatively small additional cost and would improve freeway operations.  They also feel that reconfiguration of the current loop system would improve local street operations and would be of a circulation benefit to the City as well.  Thus, Caltrans would like to include the reconfiguration of Burbank Boulevard in the overall Interstate 5 HOV project to be completed when the Burbank Boulevard Bridge is reconstructed.  They are seeking a letter of support from the City of Burbank agreeing to the reconfiguration so that they may proceed with the design.

 

In preparation for a discussion of this item, staff sent a notice of the proposed freeway and interchange modifications to all property owners, tenants, and residents of Burbank located within 1000 feet of the portion of the freeway that is planned to be realigned.

 

ANALYSIS:

 

In responding to the Caltrans proposal, staff analyzed what effect the proposed interchange reconfiguration could have on the interchange ramp intersections as well as nearby street segments and intersections that would be affected by changes in local traffic patterns.  To do this, staff evaluated the performance of both the current interchange configuration as well as the proposed diamond interchange configuration under future conditions forecasted by the City�s Travel Demand Model.  To generate future traffic volumes, staff utilized the 2025 Reduced-Growth Plus Development Opportunity Reserve Forecast developed as part of the Draft Mobility Element analysis.  This scenario assumes 51 million square feet of commercial development and 51,000 total residential units will occur by the year 2025.  The model also includes a number of regional improvements to the freeway system including the proposed HOV lanes on Interstate 5, and includes new ramps and street connections that would be in place as part of the Empire Avenue Interchange.  Inclusion of Empire Avenue in the analysis is important because the new interchange north of Burbank Boulevard causes some traffic to shift away from Burbank and use the new Empire Interchange instead.  Thus, these traffic shifts were considered when evaluating the new interchange proposed for Burbank.  Using the assumptions provided in this traffic model scenario, staff performed Level of Service (LOS) calculations on the interchange ramp intersections as well as the adjacent intersection of San Fernando Boulevard and Burbank Boulevard.  Staff also reviewed the segments of Burbank Boulevard in the interchange area to determine how the roadways would perform in 2025 under the existing and proposed interchange configuration.  In terms of effects on traffic, the proposed interchange configuration changes the way certain traffic movements are routed between Burbank Boulevard and Interstate 5 by changing some movements from free-flow, merging movements to left-turning movements controlled by traffic signals.  The configuration also changes traffic patterns at adjacent intersections which affects their LOS.

 

Evaluation of Existing and Proposed Interchange

 

City staff has analyzed the proposed diamond interchange configuration under future traffic conditions and has compared it to the existing interchange.  The proposed interchange reconfiguration would eliminate the existing free-flow, weaving, loop ramp system currently in place and add a full, signalized intersection on Burbank Boulevard between San Fernando Boulevard and the Front Street / Southbound Interstate 5 ramps signalized intersection.  The result would be a standard diamond interchange, where traffic exiting the freeway from either the north or the south could proceed either left or right on Burbank Boulevard, or could proceed straight to re-enter the freeway.  Traffic on Burbank from either direction would likewise proceed either right to access the freeway in one direction, or proceed across the overpass and turn left to access the freeway in the other direction.

 

The proposed configuration replaces free-flow and weaving movements with signalized turning movements.  Thus, northbound offramp traffic that today utilizes the northeast loop ramp to merge with Burbank Boulevard traffic would have to proceed through a signalized intersection under the new configuration.  In addition, southbound onramp free-flow traffic currently utilizing the northwest loop ramp would likewise have to proceed through a new left-turn movement at the existing Burbank/Front/southbound I-5 Ramps signalized intersection.  Under light to moderate traffic conditions, operation of the loop ramps is favorable to a diamond interchange because the loop ramp movements exhibit no delay (they are free-flow), while the diamond interchange configuration makes use of left-turn movements to move cars from Burbank Boulevard to the freeway.  However, under heavy traffic conditions, the capacity of the loop ramps is diminished by weaving conflicts and operational inefficiency.  Thus, under high-volume conditions, the proposed diamond interchange configuration would have a higher capacity than the current loop configuration.  An illustration of the existing interchange and the proposed diamond interchange is depicted on Exhibit B.

 

Staff has evaluated the performance of both the current interchange configuration as well as the proposed diamond interchange configuration under future conditions forecasted by the City�s Travel Demand Model.  Using the 2025 Reduced-Growth Plus Development Opportunity Reserve, staff performed LOS calculations on the two ramp intersections formed by the diamond interchange and compared the results to the LOS under the existing configuration.  Examination of the west intersection formed by Burbank Boulevard, Front Street, and the southbound I-5 ramps under the current interchange configuration shows that intersection to perform at LOS F at 2025 under the Reduced Growth + DOR scenario.  Under the diamond interchange proposal, where traffic from the existing northwest loop ramp is instead routed through a left-turn movement, the intersection operates in a worse LOS F condition with the addition of left-turning traffic.  However, by adding additional turn lanes to three approaches to the intersection, intersection LOS can be improved to within the City�s standard of LOS D.  Examination of the east intersection formed by Burbank Boulevard and the northbound I-5 ramps shows that the intersection operates at LOS A under the proposed diamond configuration in 2025 as compared to LOS B under the existing configuration.

 

It should be noted that an intersection LOS analysis at both the east and west intersections under the existing configuration and the new proposed diamond configuration does not take into account the inefficiency and operational issues with the weaving between the loop ramps under the current design that would be eliminated under the proposed diamond interchange.  To evaluate the future performance of the existing loop ramps, staff performed a weaving analysis of the section of roadway between the loops where ramp traffic must merge and weave with Burbank Boulevard traffic.  Under future conditions staff determined that this weaving segment would operate at LOS D.  Thus, the weaving segment formed by the loop ramps in the existing interchange configuration is predicted to operate within the City�s standards in the year 2025 under typical future traffic conditions.  However, this analysis does not take into account the safety and operational issues with these older loop ramps.  In particular, both loops are currently much tighter than current Caltrans standard, which increases the likelihood of larger vehicles and trucks leaving the roadway and rolling over, or vehicles entering the ramps at excessive speeds causing accidents.  It is for these reasons that Caltrans and FHWA desire to remove these substandard loop ramps.  Finally, while the weaving operation is predicted to operate within acceptable LOS, unanticipated future traffic increases could cause the weave to exceed capacity which would have a significant effect on interchange operations.

 

Local Street Impacts

 

In addition to an evaluation of the actual interchange ramps and intersections affected by the proposed interchange configuration, staff has reviewed the effects the proposal would have on local streets and intersections immediately adjacent to the interchange.  One local effect on circulation is the traffic shift that would occur upon relocation of the northbound onramp from Walnut Avenue (north of the interchange) to Burbank Boulevard.  This relocation causes turning movement volumes at the San Fernando Boulevard / Burbank Boulevard intersection to shift.  These shifting turn movements cause this intersection to perform at a worse level of service in 2025, from a predicted LOS D under the existing configuration to LOS E under the proposed configuration.  Staff has identified an improvement to this intersection that would improve LOS under both interchange configurations, but this improvement cannot be accomplished within existing right of way.

 

While the proposed diamond interchange does make intersection LOS at the ramp intersections and the San Fernando / Burbank intersection worse, the proposed configuration would improve operational performance of the Burbank Boulevard street segment approaching San Fernando Boulevard.  Currently, the close spacing between the northbound offramp and San Fernando Boulevard causes delay, as cars exiting the freeway who wish to proceed east on Burbank Boulevard and then north on San Fernando Boulevard must weave with cars proceeding east on Burbank Boulevard who wish to turn south on San Fernando Boulevard (towards the Burbank Town Center).  Because of the intersection spacing, this weaving movement is inefficient and can cause delay on Burbank Boulevard, especially on weekends.  Also, the short intersection spacing does not provide enough storage for vehicles traveling eastbound on Burbank Boulevard waiting at San Fernando, and cars routinely back up into the ramp intersection.  Under the new configuration, with the tightening of the ramps to the freeway mainline and the relocation of the freeway centerline to the west, the distance between the ramp intersection and the San Fernando / Burbank Boulevard intersection is increased.  This additional space better accommodates the weaving movements described above and provides more storage for vehicles waiting for the signal at San Fernando Boulevard.

 

From a traffic circulation standpoint, the proposed diamond interchange configuration provides more capacity to the interchange and improves performance under heavy traffic conditions, but does increase delays over the free-flow loop operation under light to moderate conditions because traffic movements that are free-flow today become left-turn movements in the future.  While the lane configurations proposed by Caltrans result in a worse level of service at the west ramp intersection, providing additional turn lanes to the intersection results in a level of service that operates within the City�s standards.  By tighting the ramp spacing and moving the freeway mainline to the west, spacing between the Northbound I-5 ramps and San Fernando Boulevard is increased, which provides better weaving and storage along this roadway segment.  However, relocation of the northbound onramp from Walnut Avenue to Burbank Boulevard causes the San Fernando / Burbank Boulevard intersection to operate at a poorer level of service which cannot be mitigated within available right of way.

 

A summary of intersection performance of the two ramp intersections, the ramp weaving section, and the San Fernando / Burbank intersection under both configurations is shown in Exhibit C.

 

Freeway Operations

 

Many of the transportation and circulation benefits that result from the reconfigured interchange and freeway alignment concern mainline freeway operations.  Caltrans wishes to realign the freeway centerline to eliminate the existing curves that freeway traffic makes approaching the Burbank Boulevard overpass.  Currently, sightlines around this curve, especially southbound, are constrained such that vehicles approaching the Burbank Boulevard overpass cannot see traffic ahead as they round the curve through the underpass.  This condition is exacerbated with the installation of HOV lanes as part of the freeway reconstruction project.  To accommodate the HOV lanes, the rebuilt shoulders and median will not meet standard widths for freeway design.  This condition, combined with the reduced sightlines around the curve, compromise safety of the freeway at this location.  Because the Burbank overpass must be reconstructed, Caltrans and FHWA do not wish to perpetuate these unsafe conditions and desire to rebuild the freeway to the latest safety and operational standards.  By realigning the freeway centerline, Caltrans can improve sightlines throughout the freeway corridor so that vehicles traveling in the vicinity of Burbank Boulevard will have full visibility to vehicles ahead.  Also, the realigned freeway can be rebuilt with full shoulders and medians to match the reconstructed freeway segment to the north at Empire Avenue.  Finally, with the realigned freeway, Caltrans is able to install additional auxiliary lanes on the mainline to better handle ramp traffic between Magnolia, Burbank, and Empire.

 

In addition to the safety improvements to the freeway mainline, the proposed diamond interchange will also correct the �hidden� ramp condition that exists under the current design.  Currently the northbound onramp is not located at the Burbank Boulevard interchange, but instead is located north of the intersection and is accessed via Walnut Avenue, a local street.  This presents problems to unfamiliar motorists looking for access to northbound Interstate 5 who expect to find the northbound onramp adjacent to the existing northbound offramp.  While the ramp is currently identified by signs, unfamiliar motorists looking for the northbound ramp may be misrouted to the wrong location.  Caltrans standards require that onramps and offramps be located adjacent to each other to minimize misdirected motorists and to allow vehicles who mistakenly exit the freeway to easily re-enter.  While many of Burbank�s freeway ramp systems do not share this quality, reconstruction of the Burbank Interchange would allow Caltrans to bring this intersection up to full standards.

 

 Interchange Alternatives

 

In evaluating the proposed changes to Burbank Boulevard, City and Caltrans staff evaluated alternative interchange designs that could be developed at Burbank Boulevard.  In particular, Caltrans and City staff looked at the feasibility of a Single Point Urban Interchange (SPUI) design in lieu of the diamond interchange being proposed.  This interchange has a benefit over the diamond interchange in that opposing left-turn ramp movements are consolidated into a single traffic signal in the center of the interchange instead of being accommodated in two adjacent intersections.  Consolidation of ramp movements into a single intersection can increase efficiency and capacity because opposing left turn movements can operate simultaneously instead of separately.  Caltrans feels that this design would not be optimal for Burbank Boulevard because the closely spaced intersections located on either side of the interchange at San Fernando and Front Street could interfere with the interchange and negate any potential increases in efficiency.  Also, bridge structure costs are extremely high when utilizing a single point interchange because of the way the single intersection must be constructed above the freeway.  This results in extremely long bridge spans that incur substantial additional costs.  Finally, a single point design is not conducive to bicycle and pedestrian travel across the bridge, as the large central ramp intersection gives greater vehicle conflict exposure to bicycles and pedestrians.

 

Finally, staff also reviewed the potential for retaining the northwest loop ramp that directs westbound Burbank Boulevard traffic to Southbound Interstate 5, while eliminating the northeast loop ramp and relocating the northbound onramp from Walnut to Burbank Boulevard.  This option would still allow some ramp traffic to remain in a free-flow condition and could potentially improve operations at the SB I-5/Front/Burbank intersection, while also eliminating the weaving operation.  However, under this scenario, the remaining loop ramp would prevent the mainline freeway from being straightened, which Caltrans desires for better operations on the freeway itself.  Also, this loop ramp would remain below Caltrans design standards and would still be operationally deficient.

 

CONCLUSION:

 

Caltrans is proposing to reconfigure the Burbank Boulevard Interchange and change the alignment of Interstate 5 between Magnolia Boulevard and just north of Burbank Boulevard to improve the safety and operation of the freeway mainline, and to eliminate an obsolete interchange design and add capacity to the Burbank Boulevard interchange.  This design would require two acres of city-owned right of way and two acres of private land on the west side of the freeway, and would free up an additional 6.6 acres of land on the east side of the freeway.  The proposed interchange would eliminate the existing free-flow loop ramp system and replace it with traditional intersections controlled by traffic signals.  Under future conditions, the proposed ramp intersections would operate at a slightly worse level of service than the existing design, but would still be designed to operate at LOS D or better.  The proposed configuration would remove the existing substandard loop ramps and replace them with a full diamond interchange where all traffic movements would be accommodated.  The proposal would also improve weaving and stacking distances between the interchange and San Fernando Boulevard, and would eliminate the weaving movements between the two loop ramps which could pose operational difficulties to Burbank Boulevard under heavy traffic conditions.  Finally, the proposed interchange and realignment enhances the safety and operations of the freeway mainline by providing standard sightlines, median widths, and shoulders.

 

Staff believes that, while there are tradeoffs in converting the older loop ramp system to a diamond interchange, ultimately the new interchange offers better circulation and provides more capacity at the ramp intersections.  While the loop ramps, operating under favorable traffic conditions, exhibit less delay than signalized intersections, under heavy traffic conditions these ramps can introduce delay and operational issues.  Also, the practical operation of these loop ramps is less than ideal due to their substandard radii and older design.  Staff believes that a diamond interchange with intersections operating at LOS D or better offers a better design than the current configuration, and provides the added benefit of a standard interchange system and less confusing vehicle operation.  Finally, the safety and operational benefits to the freeway mainline, particularly with regard to improving sightlines and shoulder widths, favor selection of the proposed diamond interchange over the current design.  Staff recognizes that the new design does decrease LOS of the adjacent San Fernando / Burbank intersection.  Staff recommends the City pursue options to improve this intersection, especially in light of the excess land that would become available with the installation of the diamond interchange.

 

After reviewing the proposed Caltrans interchange designs and evaluating future traffic conditions, staff believes that the City should support Caltrans in incorporating the diamond interchange design and freeway realignment into the overall Interstate 5 HOV project.  If the City Council concurs with this recommendation, staff would submit a letter to the State affirming the City�s support for the new interchange.  A draft of the proposed letter of support is included as Exhibit C.

 

RECOMMENDATION:

 

Staff recommends that the City Council direct the City Manager to submit a letter of support to Caltrans in support of reconfiguring the Burbank Boulevard Interchange to a diamond interchange as described in this report.

 

 

LIST OF EXHIBITS:

 

Exhibit A:         Proposed Interstate 5 HOV Project Right-of-Way Transactions Required for

                          Burbank Boulevard Tight Diamond Interchange

 

Exhibit B:          Schematic Illustration of Existing and Proposed Burbank Boulevard

                             Interchange

 

Exhibit C:         Analyzed Intersection Level of Service (LOS) Comparison

 

Exhibit D:         Draft Letter of Support to Caltrans

 

 

EXHIBIT A

 

 

 

EXHIBIT B

Existing and Proposed Burbank Boulevard Interchange

 Existing Interchange

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Proposed Interchange

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

EXHIBIT C

 

Analyzed Intersection Level of Service (LOS) Comparison

Note:

Interchange Improvements (rightmost column) include additional turn lanes identified by City Staff to improve Caltrans design level of service.  Identified improvements for ramp intersections (Intersections 1 and 2) would be incorporated into final design if approved.