Advisory Curve Speeds on Oregon Highways

Advisory Curve Speeds on Oregon Highways Karen Dixon Associate Professor, OSU Transportation

Research Objectives Identify the basis for the current and proposed advisory speed posting procedures for horizontal curves and passenger vehicles Identify current Oregon placement strategies at a variety of locations Identify potential future criteria for establishing advisory speeds and determine impact Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

Why Do We Care? MUTCD recently changed recommendations National Committee on Uniform Traffic Control Devices has proposed additional changes for the next edition of the MUTCD Oregon currently has one of the most conservative policies in the U.S. Transportation

Background Highlights Common Assessment Techniques include: Ball-bank indicator (Manual or Digital) Computational Approach Safe Speed Curves Other Cited Techniques (85 th -percentile, engineering judgment, engineering study, driver perception) Transportation

MUTCD Advisory Speeds Current MUTCD 16-degree for all speeds Past Procedures for ball-bank thresholds: 14-degrees (30 mph or less) 12-degrees (35 to 55 mph) 10-degrees (60 mph or more) Or: 10-degrees for all speeds Transportation

Oregon Advisory Speed Policy 13-degrees (30 mph or less) 10-degrees (35 to 55 mph) 7-degrees (60 mph or more) Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

MUTCD Advisory Speeds Future MUTCD Recommendation for passenger car -- ball-bank thresholds for: 16-degrees (30 mph or less) 14-degrees (35 to 55 mph) 12-degrees (60 mph or more) These values represent 8 to 10 mph the average driver presently exceeds current posted advisory speeds Transportation

Additional Recommendations by the National Committee on Uniform Traffic Control Devices Study based on procedures including ball-bank criteria, accelerometer readings, or calculations using equivalent side friction values (to be modified slightly) Create truck advisory speed of 12- degrees Permit staged implementation over a period of 10 to 15 years Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

Survey Results 14 Oregon County Summary 14 13 12 10 Number 8 6 4 3 4 2 0 No Response Use ball-bank No official procedures 1 1 Not applicable study required Unknow n Transportation

12 Survey Results Random Sample of Oregon Cities 12 11 10 8 Number 6 6 4 2 2 0 0 No Response Use ball-bank No official procedures Not applicable study required 0 Unknow n Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

Oregon Data Collection Plan 160 Target Sites 32 Sites per each of 5 ODOT Regions 16 State Highways per Region 16 Local Highways per Region Transportation

Summary of Sites ODOT Region State Site (curves) County Site (curves) 1 17 (19) 16 (22) 2 15 (23) 16 (30) 3 16 (23) 16 (26) 4 16 (21) 22 (30) 5 16 (18) 16 (19) Transportation

Summary of Study Locations Insert map graphic here Transportation

Manual Ball-Bank Bank Indicator Transportation

Electronic Ball-Bank Indicator Transportation

Ball-Bank Bank Indicators Mounted in Vehicle Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

How Well did the Observed Sites Comply with Current Oregon Advisory Speed Policy? Transportation

Compliance Definitions Equal To Posted Advisory Speeds were equal to recommended advisory speeds based on field ball-bank evaluations Less than or Equal To Posted Advisory Speeds were equal to or less than recommended advisory speeds based on field ball-bank evaluations Transportation

When is an Advisory Speed Plaque Needed? When the recommended advisory speed is more than 5 mph below the speed limit (in other words, 10 mph below the speed limit since we post in 5 mph intervals) Transportation

Compliance for Speeds Equal to Recommended Advisory Speed (All Curves) -- Oregon Policy Based on State Recommended Advisory Speed (mph) Manual Ballbank Readings 10 15 20 25 30 35 40 45 50 55 Total Compliance Sites 0 0 3 5 10 10 17 19 21 36 121 Total Curve Directions 0 1 5 8 26 21 36 50 26 37 210 % Compliance NA 0 60 63 38 48 47 38 81 97 58% County Recommended Advisory Speed (mph) 10 15 20 25 30 35 40 45 50 55 Total Compliance Sites 2 4 13 9 13 11 5 0 8 6 71 Total Curve Directions 5 13 28 32 46 41 36 18 16 11 246 % Compliance 40 31 46 28 28 27 14 0 50 55 29% Num bers Rounded so Totals Transportation are Approxim ate

Compliance for Speeds Equal to or Less Than Recommended Advisory Speed (All Curves) -- Oregon Policy State Recommended Advisory Speed (mph) 10 15 20 25 30 35 40 45 50 55 Total Compliance Sites 0 0 3 7 13 12 20 23 26 37 141 Total Curve Directions 0 1 5 8 26 21 36 50 26 37 210 % Compliance NA 0 60 88 50 57 56 46 100 100 67 County Recommended Advisory Speed (mph) 10 15 20 25 30 35 40 45 50 55 Total Compliance Sites 2 6 13 10 16 15 16 2 15 11 106 Total Curve Directions 5 13 28 32 46 41 36 18 16 11 246 % Compliance 40 46 46 31 35 37 44 11 94 100 43 Num bers Rounded so Totals Transportation are Approxim ate

Current Speed Plaques State Roads 54% Speed Plaque Locations Only State: 114 County: 142 County Roads 38% Total: 256 Curve Directions Plaque Posting Equal to Recommended Advisory Speed Speed Plaques Warranted State Roads County Roads 42% 32% Transportation

How Well did the Observed Sites Comply with Current and Proposed MUTCD Advisory Speed Recommendations? Transportation

State Roads Oregon 13-10-7 MUTCD 16- degree Future 16-14-12 Advisory Speed Indications Comply with (Equal To) Recommended Advisory Speeds 58% 53% 57% All Study Locations (with or without Speed Plaques) State: 210 County: 246 Total: 456 Curve Directions County Roads Oregon 13-10-7 MUTCD 16-degree Future 16-14-12 29% 38% 38% Transportation

Oregon Ball-bank Manual vs Digital Advisory Speeds 2500 2000 Radius (ft) 1500 1000 1_M_Speed 1_D_Speed Poly. (1_D_Speed) Poly. (1_M_Speed) 500 0 0 10 20 30 40 50 60 Speed (m ph) Transportation

Presentation Overview Background Information on Advisory Speeds Advisory Speed Candidate Posting Thresholds State of Practice in Oregon Data Collection and Evaluation Findings Conclusions Transportation

Summary of Findings Current Oregon Policy compliance varies, but advisory speeds of 30 to 45 mph consistently have a lower compliance Compliance defined as Equal to Recommended Advisory Speed much more rigid than a definition of Equal to or Less than Transportation

Summary of Findings Future 16-14-12 threshold at Advisory Plaque Sites okay for 35% of the sites (with 80% equal to or less than this less conservative criteria) Future 16-14-12 threshold at All Study Sites okay for 29% to 38% of the sites (using Equal To threshold) Transportation

Questions? Transportation