ASSESSING THE IMPACT OF SECURITY MEASURES AT GATES OF SEAPORTS ON TRAFFIC OPERATION Dr. Arun Chatterjee Professor Emeritus Dept of Civil & Environmental Engineering The University of Tennessee Knoxville, TN 37996-2010 E-mail: arun@utk.edu And Airton Kohls Graduate Student Dept of Civil & Environmental Engineering The University of Tennessee Knoxville, TN 37996-2010 E-mail: akohls@utk.edu And Dr. Joseph E. Hummer Professor Dept of Civil & Environmental Engineering Mann Hall NC State University Raleigh, NC 27695-7908 E-mail: hummer@eos.ncsu.edu And Dr. David B. Clarke Research Associate Professor & Director Center for Transportation Research The University of Tennessee Knoxville, TN 37996-4133 E-mail: dbclarke@utk.edu Prepared for Southeastern Transportation Center and North Carolina State Ports Authority July 2008
ABSTRACT Seaports in the USA are using a variety of security measures that include increased inspection of entering and exiting vehicles at port gates. Further, the amount of traffic is growing rapidly. The delay caused by inspection in combination with traffic growth can increase the lengths of queues of vehicles both outside and inside ports to such an extent as to cause disruption of traffic on the road network surrounding a port, and also can affect internal operations. This negative impact should be assessed in a thorough manner, and this paper presents a methodology for this purpose, which was tested using real-life data from two ports in North Carolina. The methodology involves the adaptation and use of VISSIM software, which is a microscopic simulation model. The results show that the rigorous inspection strategies in combination with traffic growth would cause queues outside port gates long enough to block and disrupt major road intersections on the surrounding road network. Simulation models can be used to assess the effectiveness of alternative strategies for alleviating congestion problems. 2
ASSESSING THE IMPACT OF SECURITY MEASURES AT GATES OF SEAPORTS ON TRAFFIC OPERATION INTRODUCTION Many seaports in the United States are experiencing major growth in both container and general cargo traffic. Increased container and general cargo traffic will move in and out through port gates, and a large portion of this freight movement will be on trucks, which will use the surrounding road systems to gain access to the ports. The efficient handling of drayage truck traffic inside as well as outside a port presents a challenge. Another challenge for seaports involves security. Since 9/11, the U.S. Department of Homeland Security (DHS) has provided funding to many seaports to implement a variety of security measures on landside and waterside. These include installation of cameras, changes in vehicle routing, increased documentation requirements for drivers and cargo, and random vehicle checks. The nature and intensity of application of these measures varies according to the national terrorism threat level. The enhanced screening of vehicles and drivers at port gates has the potential to retard the movement of trucks and railcars into and out of port facilities. When the enhanced security inspections are combined with the increased traffic demand noted above, the result may be serious traffic congestion at port gates. Traffic congestion at a port gate and the resulting queue of vehicles could cause congestion problems on the surrounding road network and also inside a port itself, and in addition to traffic delay it can have negative effects on air quality and safety. It should also be pointed out that the air quality impact of truck traffic entering and exiting ports has been a serious issue in the case of a few large ports in the US. We know of no research on the traffic operation effects of enhanced security measures at port gates. However, there has been some research work dealing with the flow of drayage truck traffic through ports and its impact on air quality and energy, and there is computer software developed by The Tioga Group and Dowling Associates for this purpose (1). It also should be acknowledged that there are a few articles that reported the use of simulation models (e.g., VISSIM) for analyzing traffic at toll plazas, and these have some similarities with our research (2). 3
Our research was undertaken to develop a methodology for investigating the traffic flow effects of enhanced security measures at port gates. We were interested in the effects on traffic flow at the port gates and on the surrounding road networks. The ports of Wilmington and Morehead City in North Carolina, which are operated by the North Carolina State Port Authority (NCSPA), were used for the case study. In addition to developing a methodology, we also tested several scenarios for the future and identified potential traffic problems. The results of this research based on the North Carolina ports may provide lessons for other ports of similar size across USA. Furthermore, it is expected that the analytical approach and experience gained from this study will be useful for analyzing traffic at other types of secure areas with high traffic volumes, such as military bases and Federal laboratories. This paper presents the methodology that was used to develop simulation models and the findings of scenario analysis, which was performed with these models DATA COLLECTION At the beginning of the study we used video cameras and manual procedures to gather data at the Port of Wilmington s South and North Gates. Later, the NCSPA set up security cameras at these port gates and at the gate to the Port of Morehead City, and the pictures recorded by video cameras were available for data retrieval. The videos captured the movement of vehicles in and out of the gates and also showed a driver s behavioral pattern with regard to selecting lanes. The cameras also gave information on service times. Additional data were provided by the Division of Highways of the North Carolina Department of Transportation (NCDOT). These data included traffic volumes at selected intersections and also information on traffic signal timing. The data retrieved from the sources above were processed and tabulated for input into the VISSIM model, which is a microscopic traffic simulation model. The data represented a weekday in September or October in 2006 and it covered the period of 7:00 AM to 6:00 PM. Various data items compiled for each port gate are described below: Aerial image for the site Geometric features of the site: 4
Layout of the port facility at guard stations and interchange gates Location of scales and x-ray screening portals Layout of the roadway system outside the port facility Routing of vehicles Types/configuration of vehicles entering and leaving the facility Vehicle speeds inside and outside the facility Number of vehicles entering and leaving the gate: Vehicles that stop at gates Vehicles that do not stop at gates Service times for each type of vehicles entering and leaving the facility at guard stations and interchange gates Traffic volumes at adjacent intersections Train schedule Signal timing at the intersection near the Morehead City port gate including detector locations and preemption strategy MODEL DEVELOPMENT To test and analyze scenarios, the study team used the VISSIM traffic simulation model (3). VISSIM is a microscopic, time-step, and behavior-based simulation model designed to analyze a full range of traffic operations. The software was developed by and is maintained by PTV Traffic Mobility Logistics. This project used version 4.3. Even though the software was not specifically developed for port entrances, some of its capabilities allow for the simulation of these types of facilities. To simulate some of the unique operations of a port, which are not explicitly included in VISSIM, certain special adjustments had to be made. Vehicle actuated programming (VAP) coding was used to simulate the different levels of inspection strategies at the guard stations. A traffic signal and a detector was set up just before the guard station and the VAP coding allowed for the entering vehicles to be counted. To represent the strategy of inspecting every N th vehicle, the signal was set initially green and after the N th vehicle passed the detector, the signal 5
would turn red and stop the next vehicle that would be inspected for a specified time. [The coding used for this purpose is available from the lead author of this article.] VISSIM allows for many types of signal controllers to be used. The virtual Econolite ASC/3 2100 module was used in the case of the intersection just outside the gate at the Morehead City port. Detailed information on traffic signal operation was necessary, including a preemption strategy for input in the virtual controller. For the development of the simulation models for Wilmington South Gate and the gate at Morehead City, 15- minute intervals were used for auto and truck traffic volumes. One-hour intervals were used for auto and truck traffic volumes for the North Gate in Wilmington. The use of fifteen-minute intervals is preferred for simulation. SOUTH GATE IN WILMINGTON The Port of Wilmington South Gate entrance is located on Shipyard Boulevard and is designated specifically for container trucks. The current conditions show traffic queues reaching the intersection with River Road, which is located 250 feet from the port entrance. Burnett Boulevard is the next major road upstream of River Road; its intersection with Shipyard Boulevard is 720 feet from the port entrance. Entering vehicles are serviced first by security guards at the gated Guard Station, which has one lane open (out of two possible lanes) for the current configuration. The layout is shown in Figure 1. Once inside the facility, passenger vehicles are diverted towards the offices and container trucks towards the Interchange Gates. The Interchange Gates are 725 feet from the Guard Station. Currently, the Interchange Gates have 4 inbound lanes, but only 3 of them are used. These three lanes have static scales. Trucks pull up and stop for paperwork, while the weight is automatically measured and transferred to the recording system. After the processing of documents, trucks move to a position downstream but close to the Interchange Gates for the inspection of chassis and container by port inspectors who look for physical damage, condition of lights, etc. Exiting vehicles also have to go through Interchange Gates. Autos go through an open by-pass lane, and container trucks use three outbound lanes with screening (x-ray) portals for radiation detection. At the Guard Station there are three outbound lanes -- one 6
open lane, one lane with x-ray portals (used by customs, if necessary), and one lane with a scale for those container trucks that may like to be weighed before leaving. NORTH GATE IN WILMINGTON The Port of Wilmington s North Gate is located at the intersection of Burnett Boulevard and Myers Boulevard, and it is designated specifically for general cargo. Due to the geometry of the adjacent roadway, and also due to the proximity of the Guard Station to the main road (Burnett Boulevard), long queues are likely to spillback along Burnett Boulevard toward Carolina Beach Road, which is a major arterial (US-421) only about one-quarter mile from the port entrance. The security procedure at the North Gate is simple but may be time consuming. The Guard Station at the North Gate is the only place where vehicles are inspected or stopped. MOREHEAD CITY GATE The gate of the port of Morehead City is located just off of US-70 (Arendell Street) and just east of downtown. Due to the intersection geometry and a rail line that serves the Port and goes through the middle of the intersection, the intersection of the port access road with US-70 has a 7-phase-plus-preemption signal controller. A two-way, single-lane road that mostly serves semi-trailer trucks leads to the Port entrance. At the Guard Station, security personnel meet an entering truck for inspection. They open the back door of a trailer and check paperwork. On their way out, vehicles are stopped at the Guard Station for checkout. Currently, problems arise at the main intersection on US-70 during the morning and mid-day peak hours. VERIFICATION OF MODEL OUTPUTS The simulation model for each gate was verified with current data before future scenarios were run. The data collection points for model outputs were positioned just after the stop signs (inbound and outbound) at the Guard Stations to provide readings of how many vehicles entered and exited each port in a one-hour period of simulation. After the warm-up time of 300 seconds, the model produced very acceptable readings for the four 7
15-minute intervals for both inbound and outbound movements. The model output values of delay and travel time also matched the respective observed values. SCENARIO ANALYSIS Scenarios for analysis were developed for different levels of security inspection at the port gates in conjunction with the 5-year cargo growth forecasts made by the NCSPA. The current service times retrieved from video data were used for all Guard Stations and the Interchange Gate. All scenarios assumed one open inbound lane at each gate. Different combinations of traffic volumes and security levels are represented by the 8 different scenarios, which are presented in Table 1. For each scenario 20 different simulation runs were performed and the variations were examined. The projected increase in truck volume from 2007 to 2012 for the South Gate in Wilmington was 102%. The projected increase in truck volume for the same period for the North Gate in Wilmington was 58%. The projected increase in truck volume from 2007 to 2012 for the Port of Morehead City was 110%. Passenger vehicle traffic volume was assumed to remain constant during this time period in all facilities. Data collection points were located in the simulation network before and after the Guard Stations to create a one-mile long travel section and record the delay experienced by drivers while entering and exiting the facilities. The values presented for delay represent the average total delay per vehicle (in seconds). The total delay is computed for every vehicle completing the travel section by subtracting the theoretical (ideal) travel time from the simulated (actual) travel time. Queue counters were positioned just upstream of the Guard Station in inbound and outbound directions respectively for all models. For the Port of Wilmington South Gate, queue counters were also positioned at the front of the Interchange Gates. The queue length was measured upstream by the simulation model at every time step. VISSIM takes a snapshot at every second of simulation time. From these values the arithmetic average is computed for every time interval. The maximum queue length for every one minute time interval was determined based on the queue lengths measured upstream at every time step (i.e., every second). Each simulation run was for one hour and included 60 one-minute intervals. 8
RESULTS South Gate at Port of Wilmington Table 2 presents the results for the Guard Station at the South Gate in Wilmington for all eight scenarios. For current traffic volume (Scenarios 1 through 4), the results show that the average queues do not interfere with the closest intersection on River Road located 250 ft upstream from the Guard Station for the current Marsec level and Marsec levels 1 and 2 (Marsec levels were previously defined in Table 1). The average queue for Marsec level 3 will interfere with the intersection at River Road and the intersection at Burnett Boulevard, which is located 720 ft upstream from the Guard Station. With current volumes, the maximum queue will block the intersection at River Road for all Marsec levels. The intersection of Shipyard Boulevard and Burnett Boulevard, will not be affected by maximum queues with the current Marsec level and levels 1 and 2. The maximum queue for Marsec level 3 will block the intersection with Burnett Boulevard. Values of delay are acceptable for the current Marsec level and for levels 1 and 2, not exceeding 90 seconds per vehicle on average. For Marsec level 3, where every vehicle is inspected for at least 2 minutes, the mean delay of 23 minutes (1,380 seconds) per vehicle is very large. The frequencies of different lengths of queue for the current traffic volume and different Marsec levels are shown in Figure 2. For the 5-year cargo growth forecast, the intersection of Shipyard Boulevard with Burnett Boulevard, located 720 ft upstream from the Guard Station, will be blocked for all Marsec levels. Values of delay per vehicle will be high for the current Marsec level and for levels 1 and 2 due to longer queues. For Marsec level 3 the average delay per vehicle will be nearly 25 minutes. The frequency of different lengths of queue with five years of growth in traffic volume is shown in Figure 3. When all vehicles are stopped (Marsec level 3), the queue length was found to exceed 5,000 feet for 44 percent of the simulation time. Actually, long queues occurred at all Marsec levels. The distance from the Guard Station to the intersection of Shipyard Boulevard with Carolina Beach Road (a major arterial, US-421) is approximately 4,500 ft. It appears that this major intersection would be adversely affected by the long queues on Shipyard Boulevard, especially by those occurring under Marsec level 3. 9
In the case of the interchange gates inside the port, Table 3 shows that the average queues for scenarios 1 through 4 (current volume levels) can be accommodated between the Guard Station and the Interchange Gates. For scenarios 1, 2, 3, 5, 6 and 7 the maximum queue will spill back to the Guard Station causing further queues and delay outside the Port. Interestingly, for Scenarios 4 and 8 at Marsec level 3--this will not happen due to long delay in the queues outside the Guard Station. No major problems were detected for the outbound lanes at the South Gate for any of the scenarios tested. North Gate in Wilmington For current truck volumes, the results presented in Table 4 for inbound traffic at the Port of Wilmington North Gate show that the average queues for the current Marsec level and for level 1 are accommodated in the auxiliary lane on Burnett Boulevard, which is 500 feet long. Marsec levels 2 and 3 will produce average queues that spill into in the travel lane on Burnett Boulevard. Maximum queue lengths for all Marsec levels will produce queues in the travel lane on Burnett Boulevard. The average delay per vehicle exceeds 20 minutes for Marsec level 3; this will be problematic. No major problems were detected for the outbound lanes for all scenarios at the North Gate. The frequency distribution of different lengths of queue length with current traffic and different Marsec levels is shown in Figure 4. When all vehicles were stopped (Marsec level 3) the maximum queue extended over 2,000 feet during 50 percent of the simulation time. For the 5-year cargo growth forecast (scenarios 5-8 in Table 4), except for the current Marsec level, the average queue lengths will create problems for traffic operations on Burnett Boulevard. The average delay per vehicle also will be high, and will exceed 20 minutes for Marsec level 3. The frequency distribution of different levels of queue length with five years of growth in traffic volume is shown in Figure 5. The distance from the Guard Station to the major intersection of Burnett Boulevard with Carolina Beach Road is 1,875 ft. This intersection would be affected adversely under Scenarios 7 and 8 (Marsec levels 2 and 3, respectively.) 10
Morehead City For the current truck volume, the results presented in Table 5 for inbound traffic at the Port of Morehead City show that the average queue did not interfere with the intersection of the Port Access Road and US-70 (located 1,140 feet upstream from the Guard Station) for the current Marsec level and for levels 1 and 2. However, the average queue will spill back about 60 feet into US-70 for Marsec level 3. The maximum queue does not interfere with the intersection of the Port Access Road and US-70 for the current Marsec level and for levels 1 and 2. The maximum queue will spill back over 500 feet into US-70 for Marsec level 3. Values of delay are excessive for all Marsec levels. No major problems were detected for the outbound lanes for all scenarios. Figure 6 shows the distribution of queue lengths for inbound traffic with current traffic volumes. When all traffic is stopped at the gate the maximum queue usually extended 1,000 feet or more. For the 5-year cargo growth forecast, Table 5 shows that the average and maximum queue lengths for inbound traffic interfere with the intersection of the Port Access Road and US-70 for all Marsec levels nearly all of the time. Values of delay also are high for all Marsec levels. Figure 7 shows the frequency distribution of queue length for inbound traffic with 5-year growth volumes. Large queues were experienced for almost all simulation runs. CONCLUDING COMMENTS The Ports of Wilmington and Morehead City in NC were used to develop a methodology for investigating the effects of enhanced security measures at port gates on traffic flow at the gates and also on roads providing access to the ports. The methodology included extensive data collection, simulation models and scenario analyses. The VISSIM simulation software proved to be an effective tool to identify likely problems and generate information so that port authorities and highway agencies can make the changes of infrastructure needed to mitigate the traffic impacts of enhanced security procedures. In the cases examined the combination of traffic growth and enhanced security will likely lead to unacceptable queuing and delay for inbound traffic. These 11
queues will impede traffic on the surrounding street network. Clearly, appropriate measures will have to be taken, such as providing additional guard stations, to bring the queues and delays back to acceptable ranges. It should be acknowledged that the seaports used for this research are relatively small in size compared to many other ports such as those in Long Beach, Los Angeles, Charleston and Savannah. The authors believe that VISSIM can be used in the case of a larger port in a similar manner to study problems related to queuing and idling of drayage trucks at port gates for different scenarios. The effort required to code, calibrate, and run VISSIM should be within the means of a port s traffic planning staff. ACKNOWLEDGEMENT The authors would like to acknowledge the financial support provided by Southeastern Transportation Center and the encouragement of Ms. DeAnna Flinchum for this project. The project also received financial support from North Carolina State Ports Authority, and the cooperation of its officials Mr. Bill Bennett, Ms. Stephanie Ayers, Mr. Doug Campen and others -- was very helpful. NC State University and the University of Tennessee provided additional financial support. Technical help was received from Dr. J. P. Moon of NC State University. REFERENCES 1. SmartWay DrayFLEET Truck Drayage Environment and Energy Model, Version 1.0 User s Guide, The Tioga Group, Inc. and Dowling Associates, Inc., Prepared for U.S. Environmental Protection Agency, June 2008. 2. Ceballos, G., and Curtis, O., Queue Analysis at Toll and Parking Exit Plazas: A Comparison between Multi-server Queuing Models and Traffic Simulation, Presented at the Annual Meeting of Institute of Transportation Engineers, Orlando, FL, August 2004 3. VISSIM User Manual. 12
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