Evidence for the Safety- Capacity Trade-Off in the Air Transportation System G. L. Donohue R. C. Haynie D. Wang J. F. Shortle Dept. of Systems Engineering & Operations Research George Mason University Fairfax, VA
Research Questions Is there a safety-capacity trade-off? What happens to safety during periods of high utilization? Safety More Safe 1.2 (Departures / Hull Loss) 1 0.8 0.6 0.4 0.2 Less Safe0 Low Capacity (Departures / Year) Hypothesized Curve High
Outline Data collection process Results from data collection Further analysis Conclusions
Wake Vortex Separation Standards Small Small 4 Nm Large 5 Nm 6 Nm 4 Nm 5 Nm Large B757 Heavy Small 5 Nm 4 Nm Heavy Large Small > 255,000 lbs 41,000 lbs to 255,000 lbs < 41,000 lbs Heavy
Atlanta Airport 2 Runways Arrivals 2 Runways Departures 50 Arrivals / Hr / RW Max 72 Seconds between Arrivals 3.1% Operations Delayed (> 15 min) Total Operations, VMC, (per 15 min) 60 50 40 30 20 10 0 T O T A L S C H E D U L E D O P E R A T I O N S A N D C U R R E N T O P T I M U M R A T E B O U N D A R I E S 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 Schedule Facility Est. Model Est. Airport Capacity Benchmark Report, FAA, 2001.
Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University. Data Collection, Atlanta Observation Point Renaissance Hotel One Hartsfield Centre Parkway Atlanta, GA Runway 26 Runway 27 ATL Airport
Data Collection Process Threshold Airplane i Airplane i+1 Runway Aircraft Type Threshold Leave Runway Heavy 10:23:14 10:24:04 Large 10:24:28 10:25:13 Large 10:26:16 10:27:12 Small 10:28:32 10:29:28......... Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
Data Manipulation Runway Occupancy Time (RTI) 45 sec Aircraft Type Threshold Leave Runway Heavy 10:23:14 10:24:04 Large 10:24:28 10:25:13 Large 10:26:16 10:27:12 Small 10:28:32 10:29:28 108 sec 77 sec = +31 sec Relative Inter-Arrival Time Inter-Arrival Time Wake Vortex Separation Standard Large following Large (3 Nm) (3 Nm / (140 knots / 3600 sec/hr))
Data Collection Summary Airport Days Observations Weather Atlanta (ATL) 3 765 VMC LaGuardia (LGA) 3 584 VMC / IMC Baltimore (BWI) 2 135 IMC Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
Results Atlanta Runway 27 Collection Day #1, VMC Relative Inter-Arrival Time Target 350 300 250 200 150 100 50 0-50 -100 Observation # (3.3 hours collection time) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University. Total Observations: 103 Arrivals / Hr: 31
Results Atlanta Runway 27 All Collection Days, VMC Lost Safety Lost Capacity 80 # Occurrences 60 40 20 0-100 -50 0 50 100 150 200 250 300 350 Relative Inter-arrival Time (sec) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
ATL Summary 20 Perfect WVSS Adherence Value = 0 # Occurrences 15 10 5 0-60 -40-20 0 20 40 60 80 100 120 140 Relative Inter-Arrival Time (sec) D1P1 36 Arr/Hr D1P1 39 Arr/Hr D2/P2 39 Arr/Hr Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University. Bin size: 20 seconds
Results LaGuardia Collection Day #2, VMC Relative Inter-Arrival Time Target 300 250 200 150 100 50 0-50 -100 Observation # (5 hours collection time) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University. Total Observations: 169 Arrivals / Hr: 33.8
Results Relative Inter-Arrival Time Target 200 175 150 125 100 75 50 25 0-25 -50-75 -100 LaGuardia Collection Day #3, IMC Observation # (3.7 hours collection time) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University. Total Observations: 126 Arrivals / Hr: 34
Comparison of Airports Aircraft Per Runway Per Hour 14 12 10 8 6 4 LGA in VMC LGA in IMC ATL in VMC ATL in VMC 2 0-2 0 50 100 150 200 250 Inter-Arrival Time (sec) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
LGA & BWI Comparison 10 Target LaGuardia VMC / IMC (4 periods, 27 34 Arrivals / Hr) Baltimore IMC (18.7 Arrivals / Hr) Observations 8 6 4 2 VFR 33.8 Arr/Hr IFR 34 Arr/Hr VFR 30.9 Arr/Hr VFR 27 Arr/Hr IFR 18.7 Arr/Hr 0-60 -20 20 60 100 140 180 220 260 Relative Inter-Arrival Time (sec) Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
15 Min Arrival Rates Atlanta Airport Collection Day #1, VMC 15 min averages Arrivals per 15 min 11:15am 1:15pm 6:45pm 8:00am 10:30am 1:00pm 3:30pm 6:00pm Individual Flight Data Average: 31 / hr
Arrival Rates 0.261 0.267 Frequency 0.153 0.148 0.074 Inter-Arrival Times During Busy 15-min Intervals (> 31 arrivals / hr) 0.0345 0.0394 0.00985 0.005 0.00985 51.4 68.9 86.3 104 121 139 156 173 191 208 226 243 261 278 Inter-Arrival Time (sec) Frequency 0.306 0.282 0.176 0.106 Inter-Arrival Times During Light 15-min Intervals (< 31 arrivals / hr) 0.0588 0.0353 0.0118 0.0118 101 141 181 221 261 301 341 381 421 Inter-Arrival Time (sec)
Safety / Capacity Relationship 120 ATL, DCA, LGA Historical Reports 1988-2001 # Reports Filed 100 80 60 40 20 NMAC RWY Inc Legal Sep 0 35 40 45 50 55 60 65 70 75 Percent Capacity Used Haynie, R.C. 2002. Ph.D. Dissertation, George Mason University.
Summary Inter-arrival times indicate frequent loss of WV separation Shape of inter-arrival distributions similar For different airports For IMC / VMC Some evidence for decline in safety for higher arrival rates Small data set (~ 1,500 points) more needed Data can be used as input to more sophisticated safety models (TOPAZ)
Backup Slides Backup Slides
Average Approach Speeds Aircraft Type Small Large B757 Heavy Avg. Approach Speed 130 knots 140 knots 140 knots 145 knots
ATL Arrival - Departure IMC 120 ASPM - April 2000 - Instrument Approaches Arrivals per Hour 100 80 60 40 20 84,90 Calculated IMC Capacity Reduced Rate (ATL) 0 0 20 40 60 80 100 120 Departures per Hour
Modeling Implications Typical Modeling Approach Safety is a constraint (Maximum rate through node in network) Capacity is metric of interest Queueing Constraints (Minimum Times Between Operations) New Approach Safety is a function of capacity / demand