CHARACTERIZING BRIDGE FUNCTIONAL OBSOLESCENCE USING CONGESTION PERFORMANCE MEASURES DETERMINED FROM ANONYMOUS PROBE VEHICLE DATA

Transcription

1 Bechtel et al. TRB #- CHARACTERIZING BRIDGE FUNCTIONAL OBSOLESCENCE USING CONGESTION PERFORMANCE MEASURES DETERMINED FROM ANONYMOUS PROBE VEHICLE DATA 0 by Andrew J. Bechtel* The College Of New Jersey 000 Pennington Road Ewing, NJ 0 (0) - bechtela@tcnj.edu Thomas M. Brennan Jr. The College of New Jersey brennant@tcnj.edu Jhenifer Mesquita de Araujo The College of New Jersey dearauj@tcnj.edu 0 *Corresponding author. bechtel@tcnj.edu Word Count:, words + * 0 words/(figure-table) = words November, 0

2 Bechtel et al. TRB #- 0 0 ABSTRACT In the last few years, anonymous probe vehicle data has become a reliable means to evaluate travel time reliability, as well as congestion conditions along highways and major arterials. The data is collected using telematics from commercial and private cellular phones, GPS devices, and on-board vehicle computers. The probe vehicle data is commercially available in one-minute increments along spatially defined roadway segments of varying lengths. This data is being incorporated into local and statewide reports to measure congestion conditions of highway and arterial systems. This paper uses crowd sourced anonymous probe vehicle data to evaluate congestion duration at functionally obsolete bridge structures. The bridges selected were functionally obsolete due to poor ratings in their deck geometry. as defined by National Bridge Inventory (NBI) rating system. These deficiencies are based on a bridge s traffic capacity as a function of its geometry and the Average Daily Traffic (ADT). These conditions are directly expected to impact the speed and volume of traffic crossing over the bridge causing congestion. An evaluation of the travel times at bridge locations was conducted to determine if a measurable amount of congestion could be observed using probe vehicle data. The methodologies presented in this paper were applied to bridge structures in Burlington County, New Jersey. Approximately million speed data records were analyzed for the bridges to measure congestion. The congestion performance measures were compared to the NBI rating to determine if congestion existed at the bridges as predicted by the NBI system. The comparison showed that a poor rating in deck geometry from the NBI system was not a strong indicator of congestion. The congestion evaluation methodologies presented in this paper where then combined with existing NBI structural ratings to demonstrate alternative bridge management strategies.

3 Bechtel et al. TRB #- 0 INTRODUCTION The American Society of Civil Engineers (ASCE) 0 Report Card for America s Infrastructure gave the country s bridges an overall grade of C +. The Federal Highway Administration (FHWA) estimates that $0. billion dollars needs to be invested annually to correct all of the deficient bridges in the US by the year 0. This is an annual increase of $ billion dollars. The ASCE cites one way to mitigate these deficient bridges is to improve asset management methodologies. Currently,.% (,) of the country s bridges are characterized as deficient (). These deficient bridges are characterized as structurally deficient or functionally obsolete, but can be both in some cases. A structurally deficient bridge requires significant maintenance, rehabilitation, or replacement. These bridges must be inspected at least every year since critical load-carrying elements were found to be in poor condition due to deterioration or damage. (). Conversely, a functionally obsolete bridge no longer meets the current standards that are used today. Examples are narrow lanes or low load-carrying capacity. (). In the United State, Bridge deficiency is determined using the Recording and Coding Guide for the Structure Inventory and Appraisal of the Nations Bridges (). The National Bridge Inventory (NBI) keeps a record of the scores that have been produced by local and state agencies. A bridge is considered structurally deficient (SD) if any of the conditions in Table are met. Table. Structurally deficient NBI scoring categories (). Categories NBI Item Number Deficiency Score Deck Condition Superstructure Substructure 0 Structural Evaluation Waterway Adequacy 0 Likewise, a bridge is categorized as Functionally Obsolete (FO) if any of the conditions in Table are met.

4 Bechtel et al. TRB #- Table. Functionally obsolete NBI scoring categories (). Categories Description NBI Item Number Deficiency Score Structural Evaluation (S) Capacity evaluation Waterway Adequacy (W) Flood evaluation Deck Geometry (D) Bridge width vs. ADT and # of lanes Under Clearances (U) Height over roadway beneath Approach Roadway Alignment (A) Angle between bridge and approach 0 Based on NBI standards, any bridge found to be structurally deficient supersedes a functionally obsolete classification. A bridge found to be functionally obsolete may be due to low scores in the structural evaluation (S) or under clearances (U), which obstruct large heavy vehicles, requiring them to choose an alternate route. This obstruction will only minimally interfere in the daily flow of traffic for the average passenger vehicle. Bridges classified as functionally obsolete due to deck geometry (D), approach roadway alignment (A), or waterway adequacy (W) have geometries or obstructions which cause a reduction in speed. Roadway geometry that differs from base condition has been shown to cause a reduction in free flow speed (). In the presence of other vehicles, this slowdown can reduce the level of service for the bridge. This reduction in service is considered congestion. A bridge determined to have poor deck geometry (D) does not have adequate width as compared to Average Daily Traffic (ADT) and lane number requirements. Poor deck geometry can also be a function of insufficient vertical clearance. A bridge with poor roadway alignment (A) is expected to require a speed reduction upon approach to improve throughput. A bridge with poor waterway adequacy (W) frequently floods, making it impassable during certain periods. All of these conditions, except lack of vertical clearance, are expected to result in a reduction in speed which can lead to congestion. An analysis of the NBI showed the individual leading cause for deficiency (including both structurally deficient and functionally obsolete bridges) was deck geometry ().

5 Bechtel et al. TRB #- 0 While the rating factors for deck geometry, road alignment, and to some extent waterway adequacy, are meant to represent areas where congestion might occur, they are in themselves not measures of congestion. The NBI uses ADT and bridge and roadway geometries to model conditions where congestion is likely. In the past it has not been economically feasible to directly measure and quantify congestion. With the recent development of regionally dispersed commercially available anonymous probe vehicle speed data, it is becoming possible to spatially and temporally evaluate congestion occurrence (). Recent studies have applied performance measures based on this data to evaluate highway corridors, crash incidents, and construction projects (,,, and ). This paper presents an evaluation of congestion for bridges categorized as functionally obsolete due to deck geometry in Burlington County, New Jersey. The evaluation consists of congestion metrics calculated from crowd sourced anonymous probe vehicle data. The congestion metrics presented are used to determine the presence, time, and the intensity of congestion at, or before, a functionally obsolete bridge. These congestion values are then compared to the NBI rankings to determine if the current bridge ranking parameters effectively convey congestion, and therefore functional obsolescence. 0 BURLINGTON COUNTY NBI DATA Burlington County, New Jersey reported bridges in the 0 NBI (Figure ). Of the bridges, can be classified as structurally deficient and can be classified as functionally obsolete. Approximately % of the bridge structures in Burlington County are deficient in some way, which is % higher than the national average. The largest cause for functional obsolescence is deck geometry ( bridges) followed by insufficient under clearances ( bridges).

6 Bechtel et al. TRB #- The bridges considered in this study are rated functionally obsolete due to their width (deck geometry). These bridges were chosen because their deficiencies are expected to impede the flow of traffic by limiting the speed and traffic capacity of the bridge. Of the bridges, 0 bridges meet this requirement for the study. However, a bridge mustt be located adjacent to a Traffic Message Channel (TMC) in order to evaluate thee congestion conditions using probe vehicle data. Of the 0 bridges, only (Figure ), are spatially located near TMCs (Table ). Many of the bridges identified in this study are located on county roads. Nationally about half of the highway bridge population is located on non-state maintained roads, and half of those are deficient in some way (). 0 Figure. NBI bridges within Burlington County, New Jersey. Table illustrates the NBI rated deficiency of each bridge. Structural Deficiency is indicatedd by SD while Functional Obsolescence is indicated by FO. The reason for the deficiency is given either by a D for Deck Geometry, a U for Under Clearances, or a DU for

7 Bechtel et al. TRB #- 0 both. Alll of the bridges given in Table are functionallyy obsolete due to their deck geometry, and none of the deck geometry problems are related to insufficient vertical clearance. All of these bridges should theoretically experiencee congestion. Table gives the rating for serviceability and functional obsolescence used in the NBI. This rating is evaluated using the deck condition (NBI Item ), structural evaluation (NBII Item ), deck geometry (NBI Item ), under clearance (NBI Item ), waterway adequacy (NBI Item ), approach road alignment (NBI Item ), ADT (NBI Item ), number of lanes (NBI Item ),, road width (NBI Item ), STRANET Highway Designationn (NBI Item 00), and vertical clearance (NBI Item ). The factor attempts to determine if a bridge has adequate capacity and clearances for legally permitted loads. It uses the bridge width and ADT to determine if the bridge can accommodate the required traffic volume. The factor is taken out of a maximum off 0, with 0 representing a high functioning bridge. Table also includes the congestion speed threshold and the total yearly congestion hours for each bridge; these values aree explained in the following section. Figure. Functionally obsolete bridges to be studiedd in Burlington County, New Jersey.

8 Bechtel et al. TRB #- Table. Functionally obsolete bridges in Burlington County, New Jersey. Congestion Structure Number Deficiency Serviceability and Functional Obsolescence Speed Threshold (MPH) Congestion Hours FO-D. FO-D. FO-DU.0 FO-D.00 FO-D. FO-D. FO-D FO-DU FO-D C0 FO-D 0. 0C0 FO-D. 0C00 FO-D.0 0C00 SD/ FO-D.00 0C0 SD/ FO-D. 0C0 FO-D. 0D00 FO-D 0. 0D0 FO-D 0.0 0D0 FO-D D0 FO-D D00 FO-D.0 0D0 FO-D D0 FO-D 0.0 0D0 FO-D D0 FO-D D0 FO-D. 0D00 FO-D.0 0D0 FO-D. 0D0 FO-D.0 0E0 SD/ FO-D.0 0G00 FO-D H00 FO-D. 0H00 SD/ FO-D H0 FO-D H0 FO-D.00 M00 FO-DU. M000 FO-D.00 M000 FO-DU.

9 Bechtel et al. TRB #- 0 CONGESTION EVALUATION Congestion at the bridge structures is determined using crowd sourced anonymous probe vehicle data. This data comes in the form of time stamped speed data for each TMC. For this study, the entire year of 0, consisting of approximately million speed records, was analyzed for each bridge in both directions. The data is sorted into -minute bins for each day of the year. Congestion is tied to a reduction in speed. In this study significant congestion was assumed to occur when speeds dropped below a defined threshold. Previous studies had used mph as the congestion threshold (). For this study, the congestion threshold speed was based on the 0th percentile space mean speed (SMS) for each TMC, and it was calculated using speed data between the hours of 000 and 000 each day (Table ). Congestion hours are determined using a binary indicator, where each SMS is compared to the congestion threshold speed calculated for each TMC. If the SMS falls below the threshold, the -minute bin it is assigned a value of ; if it is above the speed value it is assigned a value of 0. The resulting values can then be summed and divided by to calculate the congestion hours. The congestion hours can be aggregated by hour, day, month, or year. Table gives the yearly congestion hours for the functionally obsolete bridge structures. The monthly data is represented graphically in the stacked bar graph in Figure. The top 0 NBI bridges are compared to the calculated congestion hours shown in Table. 0 The bridge structures in Figure are organized in order of ascending congestion hours. Seven of the bridges studied experienced no congestion, despite being functionally obsolete due to their deck geometry. This shows that a rating of functionally obsolete due to deck geometry is not an absolute indicator of congestion. The bridge with the worst congestion is bridge. This structure experienced. congestion hours for the year of 0, and these congestion

10 Bechtel et al. TRB #- hours are consistent through each month. If there are assumed to be 00 business related travel hours a year (0 work days and peak hours a day) all but the worst bridges are congested less than 0% of the time. The 0 bridges with the worst NBI serviceability and functional obsolescence ratings are also labeled in Figure. Only out of the top 0 worst bridges in Burlington County, as ranked by the NBI, appear in the top 0 most congested bridges. There is a noticeable difference between the rating in the NBI Serviceability and Functional Obsolescence Rating and where congestion is observed. Table. Ten bridges with lowest NBI Serviceability and Sufficiency Rating NBI Rank Serviceability and Functional Obsolescence Congestion Speed Threshold (MPH) Structure Number Deficiency # 0C00 SD/ FO-D.00 # 0D0 FO-D 0.00 # 0D0 FO-D # M00 FO-DU. # FO-DU.0 # FO-DU. # 0E0 SD/ FO-D.0 # M000 FO-DU. # FO-D. # FO-D. Congestion Hours 0

11 Bechtel et al. TRB #- Bridge Number 0H0 0H00 0G00 0D0 0D0 0D D0 0D0 0D00 0C0 0C00 0C0 0D0 0C00 0D0 0D0 0H0 0H00 M C0 0D0 0C M000 M000 0E0 (NBI Rank #) No Congestion Hours (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) (NBI Rank #) January February March April May June July August Sept ember October November December Congestion Hours Figure. Monthly congestion hours for 0.

12 Bechtel et al. TRB #- BRIDGE MANAGEMENT The goal of bridge management is to get the best return on investment. In this case, the return is improved mobility and travel time reliability. This can mean a bridge can be strengthened to carry larger loads and additioinal vehicles, or it can be reconfigured to improve traffic flow. Ultimatly, there are three courses of action that an be taken when evaluating a structure: 0 0. Do nothing. Repair or retrofit the existing structure. Replace the structure. To demonstrate how congestion analysis can be used as a tool for the management of bridges, three sample structures will be evaluated. These three structures are Bridge 0C00 (most deficient bridge by NBI Rank, Table ), Bridge 0E0 (best agreement between congestion analysis and NBI, Table ), and Bridge (highest amount of measured congestion Table ). The structures will be evaluated individually, incorporating their structural condition into the process. Bridge 0C00 Bridge 0C00 is structurally deficient and functionally obsolete due to its deck geometry. It has a structural evaluation of out of 0, and a serviceability and functional obsolecence rating of out of 0. Bridge 0C00 carries a city street across the Rancocus Creek; it was constructed in 0 and improved upon in 00. Figure a shows a close-up aerial view of the bridge. The bridge serves to connect two residential areas. Figure b shows a more expansive aerial view of the bridge and its surroundings. Directly southeast of the bridge is I-. Farther to the northwest and southeast, routes 0 and both cross the Rancoucus Creek.

13 Bechtel et al. TRB #- RT 0 0C00 I- RT 0 a) Close up view of bridge b) Bridge location related to I- Figure. Aerial view of Bridgee 0C00 (0) From the congestion analysis, it has been shown that Bridge 0C00 has a total of one congestion hour per year (Table ). This being the case, the bridge adequatly handles traffic volumes. This is in contrast to the Serviceability and Functional Obsolecence Rating which is %. Based on its proximity to I- there is no need for the bridge to carry heavy truck traffic. If the bridge has vehicle weight restrictions plassed on it, there will not be a large economic impact. If the bridge were to become structurally unsafe,, the recommendation for action would be to strengthen or repair the existing structure. Due to the low number of congestion hours, there is no need to expand the bridge to carry more volume. If there is no need for expansionn there is less of a need to replace the bridge. The only reason to replace the bridge would be due to safety concerns. Bridge 0E0 Bridge 0E0 is structurally deficient and functionally obsolete due to its deck geometry. It has a structural evaluation of out of 0, and a serviceability and functional

14 Bechtel et al. TRB #- 0 obsolecence rating of out of 0. Bridge 0EA0 carries Burlington County Route across the Rancocus Creek; it was constructed in and improved upon in. Figure a shows a close-up aerial view of the bridge, and Figure bb shows an expanded view. To the south of the bridge is located a signalized intersection, and located off of the figure to the northeast is Fort Dix. Bridge 0E0 experienced. congestion hours in 0 (Table ). In order to determine when these congestionn hours occurred, a contour diagram of the average traffic speed per month over the entire day was created; this diagram is shown in Figure for both lanes of traffic (). In Figure, as the color darkens, the travel speed decreases. There are clear decreasess in both the AM and PM peak hours. The southbound lane experiences its slowest speed between 0 and AM. While the signalized intersection may cause some of the slowdown, the fact that there is slowdown and congestion in both directions would be an indicator that the bridge is influencing traffic. Since this bridge is both structurally deficient and it is causing congestion, it would be a good candidate forr replacement. Fort Dix 0E0 Intersection a) Close up view of bridge b) Bridge location related to intersection Figure. Aerial view of Bridgee 0E0 ()

15 Bechtel et al. TRB #- December November October AM Peak PM Peak -0 AM - PM Month Sept ember August July June May 0 Miles per Hour April March February January Time of Day a) Northbound lane December November AM Peak -0 AM PM Peak - PM Month October Sept ember August July June May 0 Miles per Hour April March February January Bridge Time of Day b) Southbound lane Figure. Average monthly travel speed per time of day for Bridge 0E0 Bridge carries Southbound New Jersy Route, a major arterial connecting Philadelphia to I- and the New Jersey Turnpike, over New Jersey Route (Figure ). The

16 Bechtel et al. TRB #- bridge has a structural evaluation of out of 0, and a serviceability and functional obsolecence rating of out of 0. In 0, the bridge experienced. congestion hours; this is the most out of any bridge studied (Table ). Despite this finding, it has the highest (%) Serviceability and Functional Obsolecence rating of the three bridges evaluated. Bridge runs parrellel with Bridge, which has a similar design, but onlyy experienced. congestion hours (Figure a). Figure shows the average monthly speed per time of day for Bridge. There are clear slowdowns during the AM and PM peak hours. There is greater slowdown in the PM hours than the AM hours, presumably from people leaving work in the greater Philadelphia area heading toward I- or the Turnpike. Philadelphia a) Close up view of bridge I- and NJ Turnpike b) Bridge location related to Philadelphia Figure. Aerial view of Bridge () Although Bridge is structurally adequate,, it is experiencing congestion. This congestion could possibly be due to the bridge deck geometry. However, other factors may be causing this congestion. There is a signalized intersectionn just south on New Jersey RT near a commercial shopping center, as well as a signalized intersection on East New Jersey RT. The signal operation at these points could be causing traffic slowdown that impacts speed of vehicles over the bridge. Before a recommendation for the bridgee is made, it would be prudent to perform

17 Bechtel et al. TRB #- a traffic study of the general area. If they are creating the traffic slow down, the signals can possibly be adjusted to mitigate congestion in the area. Adjusting signal timing is more cost efficient than expanding the bridge. December November AM Peak -0 AM PM Peak - PM October 0 Month Sept ember August July June May April March February January Time of Day 0 Miles per Hour Figure. Average monthly travel speed per time of day for Bridge 0 CONCLUSIONS AND FUTURE WORK The evaluation of bridge structural integrity and functional obsolesce is used as a means to determine where capital improvements should be focused. Under the current system, a bridge s functional obsolesce is partially based on NBI criteria that would indicate a bridge s inability to effectively provide the necessary capacity for the current traffic volume. The lack of traffic capacity is therefore expected to cause congestion at the bridge structures. This study applied anonymous crowd source probe vehicle data congestion analysis methodologies that are currently used to evaluate roadway performance to a sample set of bridge structures found to be functionally obsolete as defined by NBI. All of the bridges evaluated were functionally obsolete

18 Bechtel et al. TRB #- due to their deck geometries with no bridges having vertical clearance issues. The study found that although the NBI rating showed that a bridge should incur congestion; this was not necessarily the case. 0 In total, functionally obsolete bridges in Burlington County, New Jersey were evaluated using probe vehicle data for the 0 calendar year. Of the bridges, experienced no congestion hours at all. Twenty-eight bridges experienced less than 00 hours of congestion for the year, and only two bridges experienced more than 00 congestion hours with the maximum being. hours. Of the 0 worst ranked structures based on the NBI, only appeared in the 0 bridges with the worst measured congestion (Figure ). The top bridges found to have the highest measured congestion were not ranked in the NBI s top 0 worst structures (Figure / Table ). 0 An alternative bridge assessment methodology that combines the measured congestion and travel speed information obtained from probe vehicle data and the NBI structural rating was proposed. This new methodology was then used to make recommendations for three sample bridges. The congestion and speed data proved to provide insight into how the bridge is functioning beyond the NBI Serviceability and Functional Obsolescence rating. It helped provide a clear picture as to which actions to take when determining if repair or replacement were necessary. The next step in vetting this analysis method is to evaluate all of the bridges agency wide, not just the structures determined to be functionally obsolete. This will give a clear picture of how well the NBI ranking picks up bridges which are not adequately handling traffic demands. Also, an economic factor will be tied to congestion hours to evaluate the impact of increased congestion. This factor can then be weighed against the cost of multiple types of corrective measures to evaluate their cost-benefit relationships.

19 Bechtel et al. TRB #- ACKNOWLEDGMENTS The authors would like to thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Foundation - Ministry of Education of Brazil for providing funding for our undergraduate researchers. The contents of this paper reflect the views of the authors, who are responsible for the facts and the accuracy of the data presented herein, and do not necessarily reflect the official views or policies of the sponsoring organizations. These contents do not constitute a standard, specification, or regulation. The speed data and segment information used in this report was obtained from INRIX Inc.

20 Bechtel et al. TRB #- 0 LIST OF FIGURES Figure. NBI bridges in Burlington County, New Jersey Figure. Functionally obsolete bridges to be studied in Burlington County, New Jersey Figure. Monthly congestion hours for 0 Figure. Aerial view of Bridge 0C00 Figure. Aerial view of Bridge 0E0 Figure. Average monthly travel speed per time of day for Bridge 0E0 Figure. Aerial view of Bridge Figure. Average monthly travel speed per time of day for Bridge LIST OF TABLES Table. Structurally deficient NBI scoring categories Table. Functionally obsolete NBI scoring categories Table. Functionally obsolete bridges in Burlington County, New Jersey Table. Ten Bridges with lowest NBI Serviceability and Sufficiency Rating 0

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