Advisory Curve Speeds on Oregon Highways

Transcription

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

2 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

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

4 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

5 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

6 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

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

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

9 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

10 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

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

12 Survey Results 14 Oregon County Summary Number No Response Use ball-bank No official procedures 1 1 Not applicable study required Unknow n Transportation

13 12 Survey Results Random Sample of Oregon Cities Number No Response Use ball-bank No official procedures Not applicable study required 0 Unknow n Transportation

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

15 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

16 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

17 Summary of Study Locations Insert map graphic here Transportation

18 Manual Ball-Bank Bank Indicator Transportation

19 Electronic Ball-Bank Indicator Transportation

20 Ball-Bank Bank Indicators Mounted in Vehicle Transportation

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

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

23 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

24 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

25 Compliance for Speeds Equal to Recommended Advisory Speed (All Curves) -- Oregon Policy Based on State Recommended Advisory Speed (mph) Manual Ballbank Readings Total Compliance Sites Total Curve Directions % Compliance NA % County Recommended Advisory Speed (mph) Total Compliance Sites Total Curve Directions % Compliance % Num bers Rounded so Totals Transportation are Approxim ate

26 Compliance for Speeds Equal to or Less Than Recommended Advisory Speed (All Curves) -- Oregon Policy State Recommended Advisory Speed (mph) Total Compliance Sites Total Curve Directions % Compliance NA County Recommended Advisory Speed (mph) Total Compliance Sites Total Curve Directions % Compliance Num bers Rounded so Totals Transportation are Approxim ate

27 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

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

29 State Roads Oregon MUTCD 16- degree Future 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 MUTCD 16-degree Future % 38% 38% Transportation

30 Oregon Ball-bank Manual vs Digital Advisory Speeds Radius (ft) _M_Speed 1_D_Speed Poly. (1_D_Speed) Poly. (1_M_Speed) Speed (m ph) Transportation

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

32 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

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

34 Questions? Transportation