SCOTTSDALE TRANSPORTATION COMMISSION REPORT To: Transportation Commission From: Paul Basha, Transportation Director Subject: Roundabouts REVISED 12 March 2018 Meeting: 15 March 2018 Action: Information Purpose: Information pertaining to roundabout operation. Overview Attached to this memorandum is a report prepared for the City Council prior to a Study Session on 27 October 2015. This memorandum details the initial eighteen months of operation of the Hayden / Northsight roundabout installed January 2014. Also attached to this memorandum is a memorandum prepared by the Insurance Institute for Highway Safety, Highway Loss Data Institute providing answers to twelve common questions pertaining to roundabouts in the United States. Also attached to this memorandum is a roundabout information document from the Washington State Department of Transportation. Current Data Table 1 provides a comparison of daily volume, collisions, collision rates, injury collisions, and injury collision rates. (Please note all rate calculations as collisions-per-million-entering-vehicles, and are approximated to the nearest thousandth, though the percent change is calculated by the actual non-approximated value.) Table 1: Collision Statistics Comparison MEASURE SIGNAL ROUNDABOUT CHANGE Years ................................................... 2007 to 2012 .............................. 2014 to 2017 Years ............................................................ 6 .................................................. 4 Daily Volume ............................................ 27,500 ........................................ 38,500 ............................... + 40% Total Collisions ............................................ 45 ............................................... 48* .................................... + 7% Collision Rate ............................................ 0.747 .......................................... 0.860 ................................ + 15% Injury Collisions ............................................ 7 .................................................. 4 ................................... – 43% Injury Collision Rate .................................. 0.697 .......................................... 0.285 ................................ – 59% Three of the collisions occurred within five days of the roundabout opening. The fourth collision occurred three months after opening. COLLISION RATE PERIOD SIGNAL ROUNDABOUT CHANGE Weekday Peak Hour ................................. 0.911 .......................................... 0.984 .................................. + 8% Weekday Off-Peak Hour ........................... 0.806 .......................................... 0.871 .................................. + 8% Weekend ................................................... 0.465 .......................................... 0.617 ................................ + 33% INJURY COLLISION RATE PERIOD SIGNAL ROUNDABOUT CHANGE Weekday Peak Hour ................................. 0.182 .......................................... 0.041 ................................ – 77% Weekday Off-Peak Hour ........................... 0.116 .......................................... 0.041 ................................ – 64% Weekend ................................................... 0.058 .......................................... 0.083 ................................ + 43% Transportation Commission 15 March 2018 Roundabouts REVISED 12 March Page 2 of 3 These data reveal that traffic volumes have increased by more than one-third with the roundabout compared to with the traffic signal. The number of collisions and the collision rate have increased with the roundabout compared to with the signal. The number of injury collisions has decreased by less than half with the roundabout. The injury collision rate has decreased by more than half with the roundabout. These data also reveal that the collision rate increased with roundabouts compared to signals during weekday peak, weekday off-peak, and weekend periods. These data also reveal that the injury collision rate decreased substantially with roundabouts compared to signals during weekday peak and off-peak traffic periods and increased substantially during weekend traffic periods. Figure 1 depicts the driver actions by percent for both the years with signal operation and with roundabout operation. These data reveal that with the roundabout operation, the dominant collisions involve vehicles traveling around the roundabout. With the signal operation, the dominant collisions involve vehicles traveling straight with vehicles turning. Collisions involving both vehicles traveling in the same direction tend to be the least serious collisions, while collisions involving both straight and turning vehicles tend to be the most serious collisions. DRIVER ACTIONS 0% 10% 20% 30% 40% 50% 60% 70% 80% 90% All Other Straight and All Curving All Straight & Turning All Other Stopped or Slowing All Other All Other Turning SIGNAL ROUNDABOUT Figure 1: Driver Actions: Hayden / Northsight The data also revealed that with signal operation, 31% of the collisions involved drivers younger than 25 and 33% of the collisions involved drivers older than 60. With roundabout operation, 21% of the collisions involved drivers younger than 25 and 32% of the collisions involved drivers older than 60. Collisions appeared to involve younger drivers less frequently with roundabout operation, while there was no difference between signal and roundabout operation in collision involvement by older drivers. Transportation Commission 15 March 2018 Roundabouts REVISED 12 March Page 3 of 3 Figure 2 depicts Insurance Institute for Highway Safety survey information published in the Transportation Research Record in 2007. This survey revealed that 6 weeks prior to roundabout construction, roundabouts were favored by 22% to 44% of the respondents. Six weeks subsequent to roundabout construction, 48% to 67% of the respondents favored roundabouts. One to five years subsequent to roundabout construction, 57% to 87% of the respondents favored roundabouts. Insurance Institute for Highway Safety Public Opinion Survey 100% 90% 80% 70% 60% 50% 40% 30% Roundabouts Favored 20% 10% 0% Figure 2: Public Opinion Trends Relative to Roundabout Construction 6 weeks before construction 6 weeks after construction 1 to 5 years after construction Raintree Drive from Scottsdale Road to SR-101 is nearing design completion. The consultant analysis of the five (5) intersections prior to initiating design revealed that roundabouts were superior to signals at all five intersections. Table 2 provides the analyses results. Both morning and evening peak hours were analyzed which results in ten (10) possible intersection measurements. Four (4) of the intersections are full intersections with four (4) approaches, while one of the intersections has three (3) approaches. Therefore, there were a total of 38 possible approach measurements. Table 2: Future Level-of-Service and Delay Raintree Intersections Intersections at A Approaches at A Approaches at D or E Maximum Delay (10 possible) (38 possible) (38 possible) (seconds) Signal 0 5 12 59 Roundabout 10 38 0 7 Attachments: 1. Report to City Council October 27, 2015 2. © Insurance Institute for Highway Safety, Highway Loss Data Institute, 1996-2010 3. Washington State Department of Transportation Roundabout Information Department Contact: Paul Basha, 480-312-7651, [email protected] Meeting Date: October 27, 2015 General Plan Elements: Community Mobility General Plan Goals: Safely, effectively, and efficiently move people, goods, and information ACTION Presentation and discussion regarding Hayden / Northsight roundabout initial operation. CONTEXT At the June 16, 2015 City Council meeting, the Council approved right‐of‐way acquisition for Mustang Transit Improvements on 90th Street – which includes a roundabout. The Council discussed the roundabout component of the project. As a result of this discussion, the Transportation Department thought it appropriate to provide additional information on roundabout operation. NORTHSIGHT EXTENSION PURPOSE The purpose of the Northsight Boulevard Extension project was to reduce congestion at the Hayden / Frank Lloyd Wright intersection. Nine roadway options were investigated. Very detailed analyses were accomplished for three of these nine options. The selected alternative was a bypass route that directly connected Hayden Road south of Frank Lloyd Wright Boulevard to Frank Lloyd Wright Boulevard west of Hayden Road. This bypass route included a new traffic signal at the Northsight / Frank Lloyd Wright intersection and a roundabout at the Hayden / Northsight intersection. Action Taken ___________________________________________________________ City Council Report | Hayden / Northsight Roundabout Operation The purpose of the bypass route was to provide a second choice for vehicles traveling northbound on Hayden Road to travel westbound on Frank Lloyd Wright Boulevard. The goal was for the percentage of northbound‐to‐westbound left‐turns at the Hayden / Northsight intersection to reduce from 100% to between 20% and 33%. Hayden / Frank Lloyd Wright Left‐turn Volume Noon Peak Hour During the noon peak hour, 39% of the left‐turns occurred at the Hayden / Northsight intersection and 61% occurred at the Northsight / Frank Lloyd Wright intersection. There was also a 37% increase in the total number of left‐turns from Hayden Road to Frank Lloyd Wright Boulevard. Hayden / Frank Lloyd Wright Left‐turn