Roundabout Modeling in CORSIM Aaron Elias August 18 th, 2009
Objective To determine the best method of roundabout implementation in CORSIM and make recommendations for its improvement based on comparisons with field data.
Tasks 1. Field Data Collection Acquire video of two roundabout sites Extract operational parameters 2. CORSIM Simulation Network Implementation Origin-Destination Coding 3. Results Comparison Control Delay Maximum Queue 4. Conclusions and Recommendations
Field Data Collection
Site 1 Port Orchard, WA
Site 2 Lothian, MD
Data Extraction Overview Two hours of data were extracted from each of the two roundabout sites Extracted data can be grouped into two categories: Data needed for CORSIM simulation: Approach volumes Origin-Destinations Geometric information Speed data Data needed for comparison s to CORSIM output: Approach delay Maximum queue
Camera Coverage Available for Data Extraction
Site 1 Entry and Conflicting Flow Northern Approach Eastern Approach Southern Approach Time Interval Entering Flow Conflicting Flow Entering Flow Conflicting Flow Entering Flow Conflicting Flow Period 1 172 64 158 65 129 100 Period 2 187 56 139 60 111 111 Period 3 144 94 193 73 152 83 Period 4 182 57 160 74 128 103 Period 5 164 61 149 74 132 98 Period 6 180 75 158 58 117 89 Period 7 166 63 151 62 97 92 Period 8 138 58 152 61 118 84 Intersection Volume: 1855 veh. (1 st hour), 1722 veh. (2 nd hour)
Site 1 Control Delay and Queue Northern Approach Time Interval Period 1 Period 2 Period 3 Period 4 Average Delay (s) 00:09.1 00:10.3 00:12.1 00:09.4 Maximum Delay (s) 00:38.5 00:31.7 00:42.4 00:34.0 Average Queue (veh) 3.1 3.6 3.2 3.5 Maximum Queue (veh) 9 11 10 8 Eastern Approach Time Interval Period 1 Period 2 Period 3 Period 4 Average Delay (s) 00:04.2 00:03.0 00:06.7 00:06.6 Maximum Delay (s) 00:16.8 00:15.7 00:28.6 00:20.8 Average Queue (veh) 1.2 0.9 2.3 1.9 Maximum Queue (veh) 4 4 5 5
Site 2 Entry and Conflicting Flow Northern Approach Eastern Approach Southern Approach Western Approach Time Interval Entering Flow Conflicting Flow Entering Flow Conflicting Flow Entering Flow Conflicting Flow Entering Flow Conflicting Flow Period 1 171 10 94 53 50 120 10 167 Period 2 148 11 123 46 46 108 7 144 Period 3 170 14 94 49 54 124 9 172 Period 4 162 13 106 47 45 115 11 160 Period 5 187 15 98 72 73 134 13 186 Period 6 193 9 100 53 60 154 12 195 Period 7 191 16 101 65 64 129 13 183 Period 8 209 18 114 58 59 153 12 208 Intersection Volume: 1300 veh. (1 st hour), 1499 veh. (2 nd hour)
Site 2 Control Delay and Queue Northern Approach Time Interval Period 1 Period 2 Period 3 Period 4 Average Delay (s) 00:03.6 00:03.1 00:03.8 00:06.3 Maximum Delay (s) 00:17.0 00:10.6 00:12.6 00:28.4 Average Queue (veh) 1.4 1.2 1.5 2 Maximum Queue (veh) 5 4 6 9 Eastern Approach Time Interval Period 1 Period 2 Period 3 Period 4 Average Delay (s) 00:10.5 00:07.4 00:05.7 00:04.5 Maximum Delay (s) 00:40.1 00:27.5 00:29.3 00:19.7 Average Queue (veh) 1.6 1.7 1.1 1.1 Maximum Queue (veh) 9 7 5 8
CORSIM Simulation
Vehicle Entry Headway An Erlang 1 distribution was determined to be the best fit for these two roundabouts. Lothian Arrival Headway Distributions Probability 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 Arrival Headway (s) Actual Distribution Erlang 1 Distribution Port Orchard Arrival Headway Distributions Probability 0.2 0.18 0.16 0.14 0.12 0.1 0.08 0.06 0.04 0.02 0 0.0 5.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 55.0 60.0 Arrival Headway (s) Actual Distribution Erlang 1 Distribution
Network Implementation
Internal Roundabout Links
External Roundabout Approach Turn Movement Coding
Internal Roundabout Link Turn Movement Coding
Conditional Turn Movements
Origin-Destination Replication Time Period 1--2 2--3 3--4 Link 4--1 1--7 2--6 CORSIM 168 145 178 175 56 117 1 Field Data 170 147 181 177 57 117 Percent Diff. 0.90% 1.20% 1.70% 0.90% 2.50% 0.20% CORSIM 156 167 163 154 44 111 2 Field Data 152 167 157 151 43 108 Percent Diff. 2.90% 0.30% 3.80% 1.80% 1.40% 2.80% CORSIM 174 143 183 183 64 124 3 Field Data 178 143 184 181 57 129 Percent Diff. 2.40% 0.20% 0.80% 1.00% 11.10% 3.60% CORSIM 166 155 177 174 54 116 4 Field Data 160 153 175 171 56 113 Percent Diff. 3.50% 1.30% 1.40% 1.50% Example from Site 2 3.60% 2.40%
Modification to Gap Acceptance Driver Type 1 2 3 4 5 6 7 8 9 10 Default Gap Acceptance 10.0 8.8 8.0 7.2 6.4 6.0 5.6 5.2 4.8 3.6 Roundabout Gap Acceptance 8.1 6.9 6.1 5.3 4.5 4.1 3.7 3.3 2.9 1.7
Completed Network Animation
Results Comparison
Site 1 Control Delay Comparison Time Period 1 2 3 4 5 6 7 8 Control Delay (s/veh) Eastern Approach Northern Approach CORSIM Actual Percent Diff. CORSIM Actual Percent Diff. 5.1 4.2 18.70% 8.7 9.1 4.30% 3.2 3 7.40% 10.3 10.3 0.10% 8.2 6.7 20.00% 10.8 12.1 11.80% 6.6 6.6 0.40% 9.8 9.4 4.60% 5.6 6.4 13.50% 7.8 7.7 0.90% 5 3.1 47.50% 12.5 12.6 0.70% 5.7 8.5 40.20% 8.7 22.6 88.40% 5 5.2 3.20% 6.1 8.6 33.40%
Site 1 Maximum Queue Comparison Time Period 1 2 3 4 5 6 7 8 Cumulative Maximum Queues (veh) Northern Approach Southern Approach CORSIM Actual Percent Diff. CORSIM Actual Percent Diff. 8.1 9 10.50% 5.6 6 6.90% 11.4 11 3.60% 6.2 6 3.30% 11.8 11 7.00% 8.4 6 33.30% 12.2 11 10.30% 8.9 6 38.90% 12.7 11 14.30% 9.3 7 28.20% 13.7 11 21.90% 9.5 7 30.30% 13.7 14 2.20% 9.7 7 32.30% 13.8 14 1.40% 9.8 7 33.30%
Site 2 Control Delay Comparison Control Delay (s/veh) Time Period Southern Approach CORSIM Actual Percent Diff. Eastern Approach CORSIM Actual Percent Diff. 1 7.0 8.8 22.70% 6.5 10.5 46.60% 2 6.8 7.3 6.70% 7.3 7.4 0.80% 3 7.7 7.9 2.30% 5.7 5.7 0.40% 4 6.8 6.6 2.50% 6.0 4.5 28.50% 5 10.7 7.6 34.20% 7.7 4.7 47.80% 6 11.7 11.6 1.10% 6.2 8.9 35.50% 7 8.9 9.7 8.90% 6.6 8.1 20.80% 8 9.8 9.0 8.80% 7.3 6.6 10.60%
Site 2 Maximum Queue Comparison Cumulative Maximum Queues (veh) Time Period Southern Approach CORSIM Actual Percent Diff. Eastern Approach CORSIM Actual Percent Diff. 1 3.6 5.0 32.60% 5.5 9.0 48.30% 2 4.0 5.0 22.20% 7.2 9.0 22.20% 3 4.7 5.0 6.20% 7.9 9.0 13.00% 4 5.1 5.0 2.00% 8.0 9.0 11.80% 5 6.4 5.0 24.60% 8.3 9.0 8.10% 6 6.8 5.0 30.50% 8.6 9.0 4.50% 7 6.8 5.0 30.50% 8.7 9.0 3.40% 8 6.9 5.0 31.90% 8.7 9.0 3.40%
Control Delay Averages Across all Time Periods Approach Avg. CORSIM Value Avg. Field Value Percent Diff. Eastern 5.55 5.46 1.59% Northern 9.34 11.55 21.18% Southern 6.51 5.99 8.40% Site 1 Approach Avg. CORSIM Value Avg. Field Value Percent Diff. Southern 8.68 8.56 1.31% Eastern 6.66 7.05 5.65% Northern 5.48 6.13 11.21% Site 2
Summary Control delay has a wide range of error between the different periods. However, when control delay is averaged over the whole simulation, the field data and CORSIM s values are within 1 second. Maximum queue also has a wide range of error between the different periods. This is a result of when a maximum queue may occur and differences in the definition of a queued vehicle.
Conclusions
Overview CORSIM does reasonably well when predicting control delay over an average of multiple time periods. However, on a period-by-period basis it has wide ranging variability. In addition to determining the best way to model a roundabout in the current CORSIM version, this research has also made recommendations to CORSIM s developer for future releases.
Recommended CORSIM Changes: User Friendliness and Animation Ability to group nodes as a roundabout. Once grouped, circulating speed is automatically calculated based on radius and superelevation. Conditional turn movements are automatically input and internal links are coded for counterclockwise curvature. Incorporation of splitter islands into the animation.
Recommended CORSIM Changes: Traffic Simulation Ability to define the definition of a queued vehicle. Approach and time specific gap acceptance at roundabout approaches. Approach and time specific follow-up time at roundabout approaches.
Limitations of this Research Implementation of a roundabout as part of a bigger network was not modeled. CORSIM s ability to model two-lane roundabouts was not investigated.
Questions?