PURPOSE

This report is intended to apprise Council of planned modifications to the traffic signals along the Chandler Bikeway to reduce significant traffic delays on Hollywood Way and on Buena Vista Street during periods of high traffic demand.

BACKGROUND

Traffic signal operation at the intersections of Hollywood Way / Chandler Boulevard and Buena Vista Street / Chandler Boulevard was significantly changed with the implementation of the Chandler Bikeway.  Additional signal phases were added to the signal operation to insure that pedestrians and bicyclists could traverse each intersection in complete safety.  The new signal operation, however, has created two traffic issues at these signalized intersections.

1.      Signal Timing - the current traffic signal cycle is about 130 to 140 seconds long because of all the required traffic signal phases; consequently, significant traffic congestion occurs on the main streets, particularly during the evening peak travel hours.

2.      Signal Visibility - special programmed visibility (PV) traffic signal heads at the far intersection of both streets are difficult for motorists to see and recognize, resulting in driver hesitation and confusion when turning from Chandler Boulevard.  The lack of visibility adds to the traffic congestion at both intersections.

Staff proposes to reduce congestion and improve visibility by modifying the traffic operation at each intersection with the elimination of some vehicle turning movements across the bikeway.  The prohibition of turning movements across the bikeway will allow the consolidation of several traffic signal phases into one operation to reduce the total signal cycle length.  The modification will also enable elimination of the confusing PV traffic signal indications.

ANALYSIS

Current Traffic Signal Operation

The construction of the Chandler Bikeway included significant modifications to the traffic signals at Hollywood Way and at Buena Vista Street.  Special traffic signal phasing was installed to maximize the safety of bicyclists and pedestrians using the bikeway. Special phasing was installed to insure the bikeway crossings of the two streets would be free of vehicles whenever bicyclists or pedestrians are present.  Bikeway safety was the primary consideration in the development of the signal sequencing at both intersections.

Signal Timing - The resulting traffic signal operation at Chandler Boulevard and Hollywood Way or with Buena Vista Street is shown in Figure 1.  The traffic signal cycle includes four traffic movements or phases: 1) a left turn clearance interval, 2) main street green, 3) south Chandler green, and 4) north Chandler green.  The time shown for each vehicle green interval totals 124 seconds.  The pedestrian cycle can operate simultaneously with either Chandler Boulevard green, but must be proceeded by a phase to clear the bikeway crossing of vehicles that may be stored on the crossing.

The traffic signal timing was established with this configuration to insure the safety of pedestrians and bicyclists on the bikeway.  Prior to a green signal for the bikeway, a clearance interval is always given for vehicles on the bikeway to insure that no vehicles are stopped across the crosswalk.  Thus, the crosswalk should be clear of obstructions at all times when pedestrians cross.

During the peak hours, when all phasing intervals are operating at maximum, the total cycle time can reach 140 seconds.  The existing traffic signal cycle length for all other signals on Buena Vista Street and Hollywood Way is 90 seconds.  Therefore, Chandler Boulevard cannot be coordinated with other signals on the street.  The lack of coordination and the long signal cycle at Chandler Boulevard results in severe congestion in each corridor during peak travel hours.

Prior to the construction of the Chandler Boulevard Bikeway, the traffic signal operation was much simpler.  The traffic signal rotated through two 60 second long, fixed time cycles with each side of Chandler Boulevard given a green signal every other cycle.  This operation allowed the Chandler signals to be synchronized with other signals in the corridor.  The previous operation is illustrated in Figure 2.

Signal Visibility - The PV traffic signal heads are adjustable so that the signal indications appear dark from certain directions or distances from the traffic signal.  They are used at closely spaced intersections when conflicting colors (indications) may confuse motorists.  The PV heads are used at the Chandler Boulevard intersections in the north � south direction, and they are located at the farther of the two intersections from the approaching motorist.  The devices are programmed so that a driver cannot see the signal at the second intersection until he has passed the first intersection.  The complicated phasing at the crossing may show red at one signal and green at the other signal at certain times to keep vehicles from stopping on the crossing.

The PV traffic signal indications cause confusion to motorists traveling on Hollywood Way or Buena Vista Street.  The signals are programmed to be visible only within about 60 feet of the signal, and drivers become confused when they observe a dark indication.  Many drivers assume the signal is malfunctioning or broken.

Proposed Traffic Signal Operation

The existing traffic signal operation can be improved by simplifying the number of signal phasing options.  Those movements that cross the bikeway crosswalk are particularly problematic.  It is proposed to prohibit these conflicting turning movements shown in Figure 3.  With the turns across the bikeway prohibited, the traffic signal can be operated with three phases within the current 90 second cycle used along the remainder of the corridor.  Both sides on Chandler Boulevard would have a green signal at the same time.  This operation will minimize the traffic congestion that now occurs.

The traffic movements affected by the turn prohibitions are shown in Figures 4 and 5.  Figure 4 shows the turning movements to be prohibited at Buena Vista Street, and Figure 5 contains the affected traffic movements at Hollywood Way.  The turn prohibitions will impact less than 1,000 vehicles per day at each intersection, but travel will improve for more than 45,000 daily vehicles at each location.

Turn Prohibitions - Traffic displaced from the two intersections by the turn prohibitions will be relocated to nearby non-signalized crossings of the bikeway, or the traffic can use alternate routes to Burbank Boulevard or Magnolia Boulevard.  The relocated traffic will be accommodated at the unsignalized bikeway crossings or the residential street system without significant impact to pedestrians or drivers.  The turn prohibitions will be posted with appropriate signs and pavement markings at least two weeks prior to modifying the traffic signal timing, so that drivers can become used to the restrictions.

Left turn prohibitions will be identified by pavement markings, including a painted median in the center of the approach to the intersection, pavement arrows that show through and right movements only, and signage on the near side of the intersection and on the opposite side signal mast arm that show no left turn.  Right turn prohibitions currently have a red arrow signal that will be programmed to continuously show red.  Pavement markings will include through and left turn arrows, and right turn prohibition signs will be installed on the near right side of the intersection and the opposite traffic signal mast arm.

Removal of Programmed Visibility Signals - The turning movement restrictions at both intersections will also enable the removal of the PV traffic signal heads.  The PV signals were installed because of the complex overlapping signal phasing designed to keep vehicles from queuing on the bikeway.  The restrictions eliminate the complex phasing, thus making the PV signals superfluous.  These devices will be replaced with regular traffic signal indications.

We plan to implement the changes to the traffic signals in several steps to minimize driver confusion.  Turn prohibitions will be implemented first with the installation of appropriate signs and pavement markings.  The traffic signal operation will be left unchanged for two weeks to allow drivers to become accustomed to the restrictions; then, the traffic signal will be retimed.  Staff will monitor the operation of each intersection and adjust the traffic control as necessary to maintain the safest possible operation.

FISCAL IMPACT

The changes proposed to the two signalized intersections along the Chandler Bikeway will be completed with available materials and City Staff.  The improvements will have no fiscal impact.

RECOMMENDATION

Note and file.

Attachments:   Figure 1 - Existing Signal Operation

  Figure 2 � Previous Signal Operation

  Figure 3 � Proposed Signal Operation

  Figure 4 � Buena Vista Street Turning Traffic Data

  Figure 5 � Hollywood Way Turning Traffic Data

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