A ROAD SAFETY AUDIT ON A FREEWAY PROJECT IN CHINA

Transcription

1 A ROAD SAFETY AUDIT ON A FREEWAY PROJECT IN CHINA Yi Jiang, Ph.D., P.E., Associate Professor, Department of Building Construction, Management, Purdue University, West Lafayette, IN 47907, USA, jiang2@purdue.edu Maojin Lei, Director, Jiangxi Provincial Communications Scientific Research Institute, Nanchang, Jiangxi Province, China, leisen@jxjt.gov.cn Guangming Ding, Senior Engineer, Jiangxi Provincial Communications Scientific Research Institute, Nanchang, Jiangxi Province, China, dgm220@163.com Shuo Li, Ph.D., P.E, Transportation Research Engineer, Office of Research and Development, Indiana Department of Transportation, 1205 Montgomery Street, West Lafayette, Indiana 47906, USA, sli@indot.in.gov Zhongren Wang, Ph.D., P.E., Senior Transportation Engineer, Division of Traffic Operations, California Department of Transportation, 1120 N Street, Sacramento, CA 95814, USA, zhongren_wang@dot.ca.gov ABSTRACT Due to China s rapidly developing economy, nationwide highway construction in China has been adding about 4,000 kilometers of freeways each year to its system. The efficiency and mobility of the movements of people and goods have been greatly improved. However, the number and severity of traffic incidents have also increased as an inevitable byproduct of the highway system expansion. One of the effective ways of improving highway safety is a process of examining a highway project before, during, or after its construction. This process is called road safety audit. A road safety audit is a formal process, conducted by a team of qualified, properly trained, and experienced traffic safety, highway design, and other related professionals, to identify the potential problems in roadway safety. A road safety audit focuses only on safety issues and provides suggestions of remedial actions to improve the road safety based on the audit team s experience and knowledge. This paper discusses a road safety audit performed on a freeway project in China. The performed road safety audit identified the potential problems with the freeway project and provided recommendations for addressing these problems. It is emphasized in this paper that there could be potential safety problems with a highway even if the highway was designed and constructed in a total compliance with the requirements and specifications. Keywords: Freeway, Safety, Road Safety Audit, Tunnels, Bridges, Interchange 333

2 1. INTRODUCTION Due to China s rapidly developing economy, nationwide highway construction in China has been adding about 4,000 kilometers of freeways each year to its system. China s highway system has been playing an essential role in the country s rapid economic growth and considerable improvement of living standards. The efficiency and mobility of the movements of people and goods have been greatly improved. However, the number and severity of traffic incidents have also increased as an inevitable byproduct of the highway system expansion. This paper discusses a road safety audit performed on a freeway project in China. The freeway project is a section of the Xiamen-Chendu freeway. The Xiamen-Chendu freeway connects Xiamen (the capital city of Fujian province) and Chengdu (the capital city of Sichuan province). The section for safety audit is the Ruijin-Ganzhou Freeway (RGE), which is located within Jiangxi province as a part of the Xiamen-Chendu freeway. The RGE begins at Yunshi-Shan of Ruijin City and ends at Zhanggong of Ganzhou City with a total length of approximately 117 km. Map 1 shows the location of the freeway. The feasibility study of the RGE project was completed in The environmental impact assessment, economic impact analysis, and relocation analysis had been undertaken accordingly. The preliminary design of the RGE was completed and approved by the authorities. The construction of the RGE is scheduled for approximately three years from 2006 to The total construction cost is estimated to be $627 million. The RGE project consists of 78 bridges, 7 tunnels, 6 interchanges, 49 grade separations such as overpasses and underpasses, 137 drainage culverts, 185 pedestrians, 6 toll plazas, 2 service areas, 3 parking lots, and 1 main operation center. The RGE project will produce 11.8 million m 3 of earthworks and 11.7 million m 3 of stone-works. The total pavement area is m 2. It has 5.5 km of interconnecting roads, and various drainage, traffic control and safety facilities. 334

3 Map 1. The Geographical Location of the RGE (Source: the World Bank) Along with the efficiency and mobility provided, freeways in Jiangxi also have a high fatality rate, high accident severity, and huge property losses. It is estimated that the annual average number of fatality accident victims is greater than 300 on the freeway system. The direct annual cost is estimated more than RMB 30 million ($4 million), without considering the traffic delay costs. In particular, the Jiangxi highway agency has identified the following potential improvements associated with traffic safety: The freeway system consists of many tunnels. While those tunnels have not experienced major accidents, the highway agency recognizes the potential dangers. It is desired to develop an effective tunnel safety management plan. 335

4 The highway agency recognizes that the existing highway design does not adequately address the needs of some road users. For example, the presence of long vertical curves in the existing freeways does not take into account the dynamic behaviors of trucks. Effort is needed to improve the location of traffic signs and pavement markings so as to provide drivers with clear and consistent information and warning. Improvement is needed to enhance roadside safety design. To improve highway safety, the Jiangxi highway agency decided to conduct a road safety audit (RSA) on the design of the RGE. A road safety audit is a formal examination or process, conducted by a team of qualified, properly trained, and experienced traffic safety, highway design, and other related professionals, to identify the issues that may cause potential collisions. A road safety audit has proved to be an effective practice for enhancing road safety and it is most cost-effective when it is employed in the design phase. It is a proactive strategy rather than an interactive response. The road safety audit provides independent assessment and recommendations that should be considered by the client or the designer. A road safety audit focuses only on safety issues and provides opinions on the safety issues from the perspective of the potential road users based on the audit team s experience and knowledge. It does not directly address those issues of conformity to the design standards and specifications. It is not intended to re-design the project. It takes into account the human factors, combinations of design features, unusual design situations, and occurrence of unexpected circumstances that cannot be adequately addressed in the context of design process. The road safety audit presents the issues of concern, but not necessarily the solutions to the identified safety issues. 2. THE SAFETY AUDIT PROCESS To conduct the road safety audit, an audit team consisting of six members was formed. The team members were selected based on their experience and qualification related to highway operations and safety. The expertise of the team members are listed below: Team member 1: extensive experience in the general areas of freeway construction, design, and operation. Team member 2: pavement surface characteristics. Team member 3: traffic safety, automobile engineering, human factors. Team member 4: traffic safety, pavement safety characteristics. Team member 5: traffic engineering, bridge/tunnel safety, interchange/access. Team member 6: traffic signs, pavement marking, alignment, roadside safety. The audit was conducted mainly in the offices but in conjunction with site visits to the existing freeways in Jiangxi province. The audit process consisted of the following: 336

5 Obtaining Project Information The background information on the RGE was obtained from the Jiangxi Provincial Communications Department. The data and documentation include: Feasibility study report Design documents Part I Overview Part II Layout Part III - Alignment Part IV Subgrade, Pavements, and Drainage Part V Bridges and Culverts Part VI Tunnels Part VII Interchanges Part VIII Traffic Control and Ancillary Facilities Traffic data Collision data The audit team briefly reviewed the above documents and data before the kick-off meeting, so as to obtain a first insight into the RGE project and identify the further information and clarification needed. Holding a Kick-Off Meeting A kick-off meeting was held for the road safety audit. At the meeting, the team identified a list of additional documentation and data needed to conduct the road safety audit. The safety issues in previous highway projects were discussed. The audit team discussed the essential areas on which the audit should focus on. A site visit on an existing freeway was deemed necessary because of the similarities between the existing and the designed freeways. A checklist was developed by the audit team for reviewing the data and documentation collected for the audit. Assessing Data and Documents The audit was conducted in accordance with the Guidelines for a Safety Audit of Highway published by the China s Ministry of Communications (2004). The audit team also took into account the procedures, manuals, and guidelines published or reported by other countries (UKDOT 1993, Austroads 2002, TAC 2001, Wilson and Lipinski 2004, and ADB 2003) to utilize the worldwide experiences and latest techniques associated with the road safety audit. As mentioned earlier, the audit team conducted a preliminary review of the design documents and data before the kick-off meeting. After the kick-off meeting, each individual audit member assessed the design documents by focusing on their areas of expertise. After a site visit to an existing freeway during a sunny period and a rainy period, respectively, the audit team met to conduct a group review of the documents and data, and to finalize the major concerns identified during the reviewing and assessing process. 337

6 Site Visit A site visit to the selected freeway was conducted in addition to the review of design documents. This was because some potential safety problems were observed on the selected freeway and the new highway was designed in accordance with the similar standards. It was reasoned that by identifying safety problems the new highway design could be modified accordingly to eliminate these problems in the design phrase rather than after construction. Wrapping-Up the Audit The audit results and recommendations were summarized and documented in a road safety audit report for the highway agency to take necessary remedy actions. 3. FINDINGS OF THE ROAD SAFETY AUDIT Operating Speed Consistency Freeways are designed to provide for a high level of efficiency with a high safety level and to carry large traffic volumes at high speeds. In order to improve safety, it is significant to examine the consistency of the design. Design consistency can be defined as the conformance of a highway s geometric and operational features with driver expectancy (Parker 1997, Fitzpatrick, et. al. 2003). Operating speed consistency is to avoid abrupt changes in operating speeds on adjoining segments, in particular on sharp curves or steep grades or a combination of both, and therefore to provide similar sections or smooth transition. The requirements for operating speed consistency are: Good consistency: operating speed difference < 10 km/h Fair consistency: operating speed difference = km/h Poor consistency: operating speed difference > 20 km/h The operating speeds were calculated by using a set of established equations. The results indicated that the speed differences fall within a range of 5 km/h to 12.5 km/h. Therefore, the operating speed consistency can approximately be ranked as good. Design and Operating Speed Consistency Design speed is the speed employed to design highway geometrics such as vertical and horizontal curves, super-elevation, stopping distance, and so forth. Operating speed is the observed speed at which drivers are operating their vehicles during free-flow conditions. The 85th percentile of the distribution of observed speeds is used as the measure of the anticipated operating speed. In general, the design speed should be determined in terms of the highway functional class, land use, topography, and operating speed. In order to enhance safety, it is also recommended that the consistency between design and operating speeds be examined in the same segment. 338

7 It was found that the anticipated operating speeds varied from 103 km/h to 117 km/h. Since the design speed was 100 km/h, the consistency between design and operating speeds could be ranked as fair to good. It was desirable for the designers to adjust the geometric features in some identified segments with speed differences greater than 10 km/h. It should be pointed out that the operating speeds were estimated in terms of passenger cars. It was observed by the audit team that truck overloading and irregular loading were fairly common in the country. It was a concern that the speed consistency for trucks might be a problem on long grade sections. The sections with long grade were identified for possible modifications to better accommodate truck traffic. Stopping Sight Distance on Horizontal Curves Median planting, as shown in Figure 1, is typical for freeways across China, because such planting not only helps beautify the freeway, but also serves as an anti-glare screen. This practice, however, will adversely affect the available stopping sight distance for the driving lane on the outside of the horizontal curve when the median is narrow, the radius is small, and the planting is higher than driver s eyes. Figure 1. Plants in a Freeway Median Using the estimated operating speed, it was computed that in order to satisfy a required stopping sight distance of m (The Ministry of Communications 2003), the radius of the horizontal curve with median planting must be greater than 1122 m. That is to say all mainline horizontal curves with radii less than 1122 m would not be able to satisfy the minimum stopping sight distance requirement if there are plants in the median. Therefore,the audit team recommended that the design team inspect the stopping sight distances for the left lane on the outside of horizontal curves with radii less than 1122 m. 339

8 Safety Concerns on Bridges In the design documents, the amount of bridge rails and guardrails for each bridge were specified. The audit team observed on existing freeways in China that guardrails were extensively used on the roadway because the road is almost entirely built on an embankment. However, it was noticed that the guardrails on the bridged approach sections were not connected to the bridge rails on many existing freeways. Figure 2 is a photo of a typical layout of roadway guardrails and bridge rails. There exists a gap between the concrete bridge rail end and the guardrail end. The gap poses a potential danger for drivers because vehicles might hit the concrete end directly resulting in severe consequences. Therefore, AASHTO Roadside Design Guide (AASHTO 2002) specifies that guardrails must be connected to the bridge rails with transition guardrails to improve road safety. Transition guardrails gradually increase the rigidity of the guardrail so that at the connection to the bridge rail the rigidity of the guardrail is similar to that of the bridge rail. Based on the observations on the existing freeways in Jiangxi as well as in other parts of China, it is expected that guardrails would be similarly installed on the roadsides of the RGE. According to the AASHTO Highway Safety Design and Operations Guide (AASHTO 1997), research has found that crashes are seven times more likely to be fatal when the vehicle pockets or penetrates through, under, or over the barrier at the connections to a bridge end. Therefore, transitions should be provided between roadside guardrails and bridge rails. The audit team recommended that appropriate connections be installed between guardrails and bridge rails on the RGE to improve road safety. Figure 2. Space between Bridge Rail and Guardrail 340

9 Overloaded trucks were common on freeways in China. Figure 3 shows a picture of an overloaded truck on a bridge. It would be expected that the RGE would have the same problems unless regulations were effectively enforced. Overloaded trucks are especially risky with respect to bridges because the extra load could cause damages to bridge structures. Goods on the overloaded trucks generally were not packed in a safe manner. This would increase the possibility of truck overturns on bridges. Furthermore, overloaded trucks would affect the travel speeds of traffic streams. As traffic principles indicate, an inconsistent travel speed of a traffic stream is a major factor of vehicle crashes. Although it is mostly an enforcement problem, not a design or construction problem, the audit team would like to call attention to the potential risks of overloaded trucks for road and bridge safety. Safety Issues in Tunnels Similar to bridges, overloaded trucks are also a concern for tunnel safety. In addition, trucks with oversized loads, as the one shown in Fig. 4, should also be a concern for tunnels because tunnels have limited horizontal and vertical clearances. Overloaded and oversized trucks should be effectively regulated to minimize the chances of accidents within tunnels. Figure 3. Overloaded Truck on Bridge 341

10 Figure 4. A Truck with Oversized Load It was observed that on existing freeways some vehicles changed lanes to pass other vehicles within tunnels. Because of limited space, any accident inside a tunnel could cause severe consequences to the tunnel structure as well as to the highway system. Changing lanes inside tunnels must be prohibited to minimize the probability of crashes. To achieve this, signs should be designed and posted before each tunnel to warn drivers not to change lanes or pass other vehicles inside the tunnel. Lighting is important for traffic safety of tunnels, especially for the safety of long tunnels. It was observed that for unknown reasons only some of the lights were turned on in the tunnels on the freeway shown in Figure 5. Actions should be taken for the RGE tunnel to assure that all lights are lighted during operation unless the design requirements indicate to use portion of the lighting fixtures. Figure 5. Only Some Lights Are on in the Tunnel 342

11 Safety Issues at Interchanges There will be six interchanges in the RGE project. The design documents for interchanges were examined by the audit team to verify their appropriateness in terms of road safety. To minimize the effect of adjacent interchanges on traffic flow and safety, the distances between adjacent interchanges should be greater than 3 km. The distances between the adjacent designed interchanges are all more than 10 km so that the traffic flow of an interchange will not be directly affected by the vehicle maneuvers at other interchanges. That is, the spacing between the interchanges will not be a problem related to traffic safety. The audit team reviewed the geometrics on the design documents related to interchanges. Sight distances to the exit and gore areas are satisfactorily designed. Sight distances to the entry and merge areas are also satisfactorily designed. The lengths and cross-sections of auxiliary lanes meet the standards. There are no problems with the lane continuity of the interchanges. The ramp geometrics and cross-sections do not reveal any inadequate or inappropriate designs. The types of the designed interchanges are similar so that the patterns of the exit and entry ramps are not different to drivers. The consistency of the exit and entry patterns among the interchanges is important for road safety. With the consistent ramp patterns the drivers do not need to spend extra time to understand the new patterns and to execute new driving maneuvers while passing a different interchange. Based on the vertical and horizontal geometrics of the intersections, the operating speeds were found to satisfy the speed consistency requirements. In the design documents, it is specified to plant grasses and trees in the enclosed areas between the intersecting roadways and the ramps. While grasses are essential to control soil erosion, trees in the enclosed areas may pose potential safety risks. First, trees near roadway may become dangerous obstacles for off-course vehicles. Second, trees may block drivers views for the vehicles on the mainline and on the ramp to see each other before merging. Therefore, trees may create unsafe driving conditions for vehicles at interchanges, especially for the merging vehicles. To minimize any possible hazard to drivers, it is recommended that trees not be planted in the enclosed areas between the intersecting roadways and the ramps. Grasses should be planted as designed. As an option, flowers could be planted in addition to grasses. Based on the field visit to the existing freeways and the observations of other freeways in China, the following additional issues should be considered for the interchanges in the RGE projects. In some of the ramp gore areas, crash cushions were utilized as barrier end protection as shown in Figure 6. However, some problems were observed with the use of crash cushions. First, the number of crash cushions seemed to be insufficient as compared to the crash cushions used in the USA. The number of crash cushions should be determined according to standards such as the AASHTO Roadside Design Guide (AASHTO 2002). Second, the sizes (height and diameter) 343

12 of the crash cushions seemed to be smaller than the sizes of those used in the USA. Figure 6. Crash Cushions in an Interchange Gore Area Third, the crash cushions were not covered with lids as illustrated in Figure 7. This may result in an increase, decrease, or change of the content inside the cushions and thus the cushions may not function as intended. Normally, the crash cushions should be filled with sand and should be free of other materials. However, as can be seen in Figure 7, the crash cushions contained many unintended materials. Based on these observations, the audit team concluded that it would be a worthy and positive effort for further enhancing road safety if the use of crash cushions in the RGE project would follow either China s established standards or the AASHTO Roadside Design Guide (AASHTO 2002). Figure 7. Crash Cushions without Cover 344

13 As a common practice in China, guardrails are extensively used in freeway roadsides and in many cases curbs are typically installed with guardrails. Figure 8 shows a typical case of curbs used along with guardrails in the median on a freeway. However, as specified in the Standards used in the USA (AASHTO 2002 and INDOT 2006), roadways with a design speed greater than 70 km/h should be designed without curbs. The use of curbs with a roadside barrier, such as guardrails, is discouraged in the USA, because it has been found that curbs offer no safety benefits on high-speed roadways. It is believed that curbs on high-speed roadways will increase the risks for vehicles to overturn after impact. In a system with curbs and guardrails, an off-course vehicle would hit the curb first and then the vehicle would be in the process of overturning when hitting the guardrail. Thus, the vehicle would most likely impact the guardrail at an angle and a position that would be more harmful to the vehicle. Bridge piers are the most important component of a bridge structure. It is essential for the freeway system that the piers of interchange bridges be adequately protected. Figure 9 is an example of pier protection. The curbs under the bridge would cause vehicles to overturn and thus would increase the chances of a vehicle fire. Consequently, vehicle burning could result in more damages to the bridge piers and other structure components. Therefore, curbs should not be used for pier protection. Instead, guardrails or crash cushions can be placed to protect bridge piers. However, guardrails and crash cushions must be appropriately designed and placed to adequately protect bridge piers. Figure 8. Curbs and Guardrails in the Median 345

14 Figure 9. Curbs under an Interchange Bridge 4. SUMMARY AND CONCLUSIONS The road safety audit on the designed freeway was successfully performed. The audit team not only reviewed the design documents, but also visited existing freeways to identify potential safety problems in the design. Through the road safety audit, the following safety concerns were identified: The design s estimated speed consistency was satisfactory in terms of passenger cars. However, because truck overloading and irregular loading were common in the country, the speed consistency for trucks could be a concern on sections with long grades. Median planting is not recommended for segments with narrow median and small horizontal curve radii, because plants may adversely influence the stopping sight distance on the outside lanes of the horizontal curves. Truck overloading and irregular loading were a common phenomenon in the country. It is a great challenge to take into account this phenomenon in the freeway design. The use of curbs on freeways is not recommended because wheel contact with a curb may cause a vehicle to overturn and become airborne. If used, the design should provide specific requirements and safety analysis. Appropriate transitions should be provided between roadside guardrails and bridge rails. The audit team recommended that appropriate connections be installed between guardrails and bridge rails to eliminate gaps and improve road safety. 346

15 Actions should be taken to assure that all lights are lighted during operation in tunnels unless the design requirements indicate to use only portions of the lighting fixtures. To minimize any possible hazard to drivers, it was recommended that trees not be planted in the enclosed areas between the intersecting roadways and the ramps. Grasses should be planted as designed. As an option, flowers could be planted in addition to grasses. The guardrail ends at ramp gore areas should protected using crash cushions. The design of crash cushions should be undertaken to determine the appropriate number and size of crash cushions. The cushions should be covered. In the process of conducting the road safety audit, the audit team was impressed and motivated by the emphasis of Jiangxi Provincial Communications Department on the traffic safety and the strong support from Jiangxi Provincial High-Class Highway Administration Bureau. The team spirit of the audit team members also played an important role in completing the audit successfully. The audit team deemed the road safety audit on the design necessary and important. Necessary actions should be taken accordingly to improve the design and to mitigate the potential safety problems in future operations. 5. REFERENCES AASHTO (2001). A Policy on Geometric Design of Highways and Streets, American Association of State Highway and Transportation Officials, Washington, DC. AASHTO (2002). Roadside Design Guide, American Association of State Highway and Transportation Officials, Washington, DC. Asian Development Bank (ADB) (2003), Road Safety Audit for Road Projects - An Operational Tool Kit, Manila, Philippines. Austroads (2002), Austroads Road Safety Audit, 2 nd Edition (AP-G30/2). Fitzpatrick, K., Carlson, P., Brewer, M. A., Wooldridge, M. D., and Miaou, S. (2003). Design Speed, Operating Speed, and Posted Speed Practices, NCHRP Report 504, Transportation Research Board, Washington, DC. Indiana Department of Transportation (INDOT). (2006). Road Design Standard Chapter 49: Roadside Safety. Indianapolis, Indiana, USA. Parker, M. R. (1997). Effects of Raising and Lowering Speed Limits on Selected Roadway Sections, FHWA-RD Final Report, Federal Highway Administration, Washington, DC. The Ministry of Communications (1994). Design Specification for Highway Route, JTJ , Beijing, China. The Ministry of Communications (2003), Technical Standard of Highway Engineering, JTG B , Beijing, China. 347

16 The Ministry of Communications (2004). Guidelines for a Safety Audit of Highway, JTG/T B ,Beijing, China. Transportation Association of Canada (TAC) (2001). The Canadian Road Safety Audit Guide, Ottawa, ON, Canada. UK Department of Transportation (UKDOT) (1993). Design Manual for Roads and Bridges, Road Safety Audits, Part 2, HD 19/03, Vol. 5, Section 2, South Ruislip, Middlesex. Wilson, E. M. and Lipinski, M. E. (2004), Road Safety Audits, NCHRP Synthesis 336, Transportation Research Board, Washington, D.C. 348