IMPACT OF WORK ZONES ON SPEED VARIATION DURING WIDENING OF THE HIGHWAY A CASE STUDY

Transcription

1 IMPACT OF WORK ZONES ON SPEED VARIATION DURING WIDENING OF THE HIGHWAY A CASE STUDY VIDYA. R PhD Scholar, Department of Civil Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu , India vidyarajesh123@gmail.com Dr.S.MOSES SANTHAKUMAR Professor & Head, Department of Civil Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu , India Dr.SAMSON MATHEW Associate Professor, Department of Civil Engineering, National Institute of Technology, Tiruchirappalli, Tamil Nadu , India Abstract: Reconstruction and rehabilitation of highways are vital for the infrastructure development of the country, meeting the transportation demands of the increasing population. Therefore Construction work zones are inevitable, during which, lane closures and diversions are necessary. Many work zones are not adequately designed resulting in delay and drastic speed reduction which increases vehicle operating costs as well as delay costs. Hence, the strategies for traffic and work zone management should be concentrated upon for ensuring safety, comfort and speed. The research aims to study and assess the impact of work zones on Speed characteristics during widening of a highway. The variation of speed in different construction work zones is analysed during different construction stages in different stretches with a case study of the Four Laning project of Trichy-Thanjavur Section of the NH-67. An analysis of variance confirms that the differences in mean speeds are statistically significant in the approach zone and terminal transition zone at the 95% confidence level both in stage II and stage III respectively. Keywords: Construction Stages; Four laning; Work zone. 1. Introduction In a developing Country like India, it is necessary to meet the expectations of growing demand with the increasing population. It paves way to Construction and reconstruction of transportation Infrastructure. In this process Construction work zones are inevitable. It becomes necessary to study their impacts and operational issues. Speed delays, bottlenecks, accidents are more pronounced during reconstruction activities in construction work zones, analysing the impacts of the work zones and formulation of strategies is vital for effective Management and safety of road users. Despite the efforts made by government agencies and the highway authorities, there are great queuing scenarios causing huge time delay, additional incurrence of vehicle operating costs and work zone crashes. The procedures and strategies involved for traffic and work zone management are not adequate. It requires proper documentation for efficient decision making process addressing the present shortcomings. Lane rental practices are adopted in developed countries. Numerous researchers have investigated the traffic flow characteristics till date. [Nemeth and Rathi (1985)] studied the potential impact of speed reduction at freeway lane closures. [Memmott and Dudek (1985)] developed a computer model, QUEWZ, to estimate the user costs caused by lane closures. [Nader and Azadivar (1992)] studied the traffic behavior at freeway work zones and came up with the recommendations for the control procedures at such sites. [Krammes and Lopez (1992)] offered some recommendations to estimate the capacities of short-term freeway work zone lane closures.[dixon et al. (1996)] studied 24 work zones in North Carolina. They analyzed speed flow behaviour based on site condition, lane flow configuration, and intensity of work activity. [Martinelli and Xu (1996)] estimated the traffic delay in freeway work zone in terms of speed reduction and congestion delay. [Jiang (1999)] analyzed the traffic data collected from Indiana four lane freeways and based on their investigations and defined capacity as traffic flow rate just before a sharp speed drop followed by sustained low vehicle speed and traffic flow fluctuation. [Carr (2000)] studied that a work zone can produce three types of ISSN : Vol. 4 No.02 February

2 delay associated with time costs: Speed delay, Backup delay and Diversion delay. [Kim et al. (2001)] developed a multiple regression model for right and left lane closure. [Chen et al. (2002)] developed a mathematical model to optimize work zone lengths on four-lane highways, where one lane in one direction was closed at a time. [Adeli and Jiang (2003)] proposed a model combined fuzzy logic with neural network to estimate freeway work zone capacity. [Benekohal et al. (2003)] developed speed flow curves suitable for work zones based on the field data for determining the operating speed. 30 hours of data from 11 work zone locations were collected. A new approach towards work zone capacity estimation is established based on these relationships. [Sun and Benekohal (2004)] investigated platooning and gap characteristics of short-term and long-term freeway work zones. [Chen and Paul Schonfeld (2005)] have evaluated several alternatives defined by the number of closed lanes, fractions of traffic diverted to alternate routes, and crossover of diverted traffic to opposite lanes. [Chatterjee et al. (2009)] developed a simple method for choosing appropriate values of driving behaviour parameters in the VISSIM micro-simulation model to match the desired field capacity for work zones operating in a typical early merge system. Although vast research had been carried about the traffic characteristic in general, very little attention has been paid to the same in the construction work zones owing to the context of Indian traffic conditions. An attempt has been made to study the traffic characteristics and to test for significant differences in the change in mean speeds of the vehicles in different components of works zones of varying lengths during different stages of construction. This necessitates the need to study the characteristics further in detail for understanding the traffic behaviour. 2. Construction work zone Work Zone is defined as an area of a highway in which maintenance and construction operations are taking place that impinge on the number of lanes available to traffic or affect the operational characteristics of traffic flowing through the area. [Highway Capacity Manual 2000)].The Components of Traffic Control Areas of work zone as per Indian Road Congress, IRC SP 55 which gives the guidelines on road safety in construction zones are shown in Fig. 1. The Individual work zone components as observed in the field are depicted in Fig. 2. Fig. 1. Components of Traffic Control Areas in Construction Zone. Source:[IRC: SP: ] ISSN : Vol. 4 No.02 February

3 The Construction Zone consists of four zones as described below: 1. Advance Warning Zone: The Advance Warning Zone is the zone werein the the road users are informed about the work ahead and gives indication regarding the speed reduction through traffic signs. 2.Approach Transition Zone:The Approach Transition Zone is the zone werein the road users are made to move on the guided pathway. 3.Activity Area:The activity area is the zone where the actual work is carried out. 4.Terminal Transition Zone: Terminal Transition Zone is the zone were the road users return to the Normal Path. (a) Advance Warning Zone (b) Approach Transition Zone (c) Activity Zone (d) Terminal Transition Zone Fig. 2. The Work zone Components as observed in the field. ISSN : Vol. 4 No.02 February

4 3. Methodology Before selecting the sites, they were categorized according to the different stages of construction. Hence, the whole section of the Highway was categorized into different construction stages: Stage I: Involves Extension of Shoulders on both sides and the vehicles moving in the original 2-lane road. Stage II: Vehicles moving in the restricted Part of the original two lane road that is one lane closed and piles on the adjacent road. Stage III: Vehicles moving in the restricted part of the new 2-lane road.once the Construction of one lane which was closed in Stage II is over, the traffic is diverted to the newly constructed lane, and the adjacent lane is the work zone. Stage IV Both Lanes are opened to traffic. The different stages of widening of the existing two lanes into four lanes generally adopted are shown in Fig. 3. Lane closed for construction. Constructed lane opened for traffic (a) Stage I (b) Stage II Construction work going on in the next lane (c) Stage III (d) Stage IV Fig 3. Different Stages of Construction during widening of a Highways. ISSN : Vol. 4 No.02 February

5 4. Work zone characteristics and data collection The Thanjavur (Ch ) to Trichy (Ch ) section of the National Highway 67 is of Km. length and connects the two districts Tiruchirappalli and Thanjavur in Tamil Nadu.This section of highway serves the people of industrial area of Bharat Heavy Electricals Limited (BHEL), the students and staffs of National Institute of Technology (NIT) and SASTRA University, Vallam, villages like Assur, Pudukudi, Kattur, and many more rural settlements. This section contains two railway crossings (one at Ariyamangalam and the other at Tiruverumbur), one major by-pass at Vallam and around 30 other small bridges and culverts. The work zone sites are located along NH 67 of Trichy-Tanjavur section during four laning project of widening of highway. In the four laning of National Highways, not all the stretches are constructed uniformly. Some of the stretches are constructed earlier while some later. This non-uniformity of the construction depends on the site selection for that particular stage of construction.hence, before conducting surveys, it is necessary to know the stage of construction going on. The surveys were taken at seven different work zone sites during three stages of construction in four work zone components. After the selection of sites of appropriate length, width, and the site measurements of the stretches were taken. Spot Speed Surveys were carried out in the selected sites of rural and urban areas to know the speed variation in different Components. The observations for the spot speed were taken at the mid-length of the different Components for one hour duration.after, conducting the surveys at selected sites, the data collected were analyzed. The data was collected for 4 major types namely Bus, Car, Jeep Van (C/J/V), Two Wheeler (TW) and Truck. From the traffic composition of various vehicle types, it is observed that two wheelers contribute major proportion with a average proportion ranging from 44%- 53%, Buses occupy a share of 7-11%, C/J/V constitute 26-31% of the total traffic and the slow moving traffic (cycles, cycle rickshaws, etc.) constitute 1-4 % of the traffic. The average spot speed of different categories of vehicles in different components of the work zones are in stages I, II and III are given in Table 1, 2 and 3 respectively. The Table 1 shows that the Speed is higher in Stage I as Compared to Stage II and Stage III, since the stage I comprise only of Shoulder widening and the lane constriction has not commenced. It can be observed from the Table 2 and 3 that the speed of the vehicles drops considerably while passing through the transition area from the advance warning zone and then decreases further in the activity zone and increases again in the terminal transition zone. It can also be seen that the most of the vehicles in Advance Warning zone are moving in a speed of km/h while most of them are moving with a speed of km/h in Transition zone, km/h in Activity zone and km/h in the Termination zone. Table 1. The average Spot speed of different categories of vehicles in different Work Sites of stage I. Work Sites Average Spot Speed (Kph) BUS C/J/V TW TRUCK ISSN : Vol. 4 No.02 February

6 Table 2. The average spot speed of different categories of vehicles in different work sites of stage II. Work Sites Advance warning area Approach Transition Area Average Speed (Kph) Activity area Terminal Transition Area BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK ISSN : Vol. 4 No.02 February

7 Table 3. The average spot speed of different categories of vehicles in different Work Sites of stage III. Work Sites Advance warning area Approach Transition Area Average Speed (Kph) Activity area Terminal Transition Area BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK BUS C/J/V TW TRUCK ISSN : Vol. 4 No.02 February

8 The variations of speed in work zone components in stage II and stage III are shown in Fig. 4. Fig. 4. Speed Variation in different work zone Components. To study the reduction of speed due to work zones, an analysis of variance (ANOVA) was conducted. The ANOVA tests whether or not the speeds are the same among the two zones viz., advance warning zone and terminal transition zone: H O : µ 1 =µ 2, Ha: µ 1 µ 2, where, μi are the mean speed in the two zones. The results from ANOVA analysis are presented in Table 4. The results of this analysis indicate that the the differences in mean speeds are statistically significant in the two zones at the 95% confidence level both in stages II and III respectively and further, a P-value in all vehicle categories indicate that the null hypothesis should be rejected at the 0.05 level of significance. Table.4 ANOVA test for change in speed during Stage II and stage III. Stage Bus Car TW Truck II F value p value 2.5 E E E E-06 III F value p value 1.52 E E E E-05 F critical Conclusions The variation of speed of the vehicles in different components of works zones of varying lengths during different stages of construction is studied. The observations made from the various surveys conducted in the different sites during different stages are summarized below: It was observed that there was speed reduction in different category of vehicles from Stage-I to II due to the transition zones and newly laid road caused increase in speeds in stage III. The speed of the vehicle drops significantly while entering the construction zone. On the basis of the results from the study, speed of the vehicle is more in the advance warning zone and decreases as it enters the approach transition zone and then decreases further in the activity zone and increases again in the terminal transition zone. The average speed of the vehicles at the transition zone of the construction area was reduced by 60 % of the speed at the advance warning area. ISSN : Vol. 4 No.02 February

9 A statistical analysis confirms the differences in mean speeds are statistically significant in the advance warning zone and terminal transition zone in all vehicle categories at the 95% confidence level both in stage II and stage III respectively in spite of increase in mean speed in stage III. Proper Pavement management of work zones which is overlooked during operations of reconstruction should be rectified and guidelines for work zones operations should be strengthened ensuring safety, comfort and speed. This requires an insight based on specific characteristics of site and location. It is vital to concentrate on counter measures through further research. Speed being the vital factor affecting the delay as well as the safety of the workers in the work zone has its own significance. There will be drop in speed of the vehicles in the construction zone which will end up in congestion delays and queue lengths of greater magnitude if not properly addressed. References [1] Adeli, H.; Jiang, X. (2003): Neuro-Fuzzy Logic Model for Freeway Work Zone Capacity Estimation. Journal of Transportation Engineering, 129(5), pp [2] Benekohal, R. F.; Kaja-Mohideen A.; Chitturi, M. (2003): Evaluation of Construction Work Zone Operational Issues: Capacity, Queue, and Delay. Report No. ITRC FR 00/01-4. Department of Civil and Environmental Engineering (UIUC). [3] Carr, R. I. (2000): Construction Congestion Cost (CO 3 ) Basic Model. Journal of Construction Engineering and Management, 126(2), pp [4] Chatterjee, I.; Edara, P.; Menneni, S.; Sun, C. (2009): Replication of Work Zone Capacities in a Simulation Model. Transportation Research Record: Journal of the Transportation Research Board, No. 2130, pp [5] Chen, S.; Tang, Y.; Schonfeld, P. (2002): Optimizing work zones for two-lane highway maintenance projects. Journal of Transportation Engineering, 128(2), pp [6] Chen, C., and Schonfeld, P. (2005): Work zone lengths for a four-lane road with an alternate route. Journal of Transportation Engineering, 131(10), pp [7] Dixon, K.; Hummer, J. E.; Lorscheider, A. R. (1996): Capacity for North Carolina Freeway Work Zones. Transportation Research Record 1529, Transportation Research Board, Washington, D.C. [8] Highway Capacity Manual. (2000). TRB, National Research Council, Washington, D.C. [9] Indian Road Congress (IRC) (2001): Guidelines on Safety in Road Construction Zones.IRC SP: 55, New Delhi, India. [10] Jiang, Y. (1999): Traffic Capacity, Speed, and Queue-Discharge Rate of Indiana s Four-Lane Freeway Work Zones. Transportation Research Record 1657.Transportation Research Board, Washington, D.C, pp [11] Kim, T.; Lovell, D.J. Paracha. (2001): A New Methodology to Estimate Capacity for Freeway Work Zones. Paper No [12] Krammes, R. A.; G. O. Lopez. (1992): Updated Short-Term Freeway Work Zone Lane Closure Capacity Values. Report FHWA/TX-92/1108-5, Federal Highway Administration, U.S. Department of Transportation, and Texas Department of Transportation, Austin, Texas. [13] Martinelli, D. R.; Xu, D. (1996): Delay Estimation and Optional Length for Four-Lane Divided Work Zones. Journal of Transportation Engineering, 122(2), pp [14] Memmott, J.L.; Dudek, C.L. (1984): Queue and User Cost Evaluation of Work Zones. Transportation Research Record 869, Transportation Research Board, Washington, D.C. [15] Nader Afshar.; Farhad Azadivar. (1992): A Simulation Study of Traffic Control Procedures at Highway Work Zones. Proc. Winter Simulation Conference. [16] Nemeth, Z. A.; Rathi, A. K. (1985): Potential Impact of Speed Reduction at Freeway Lane Closures: A Simulation Study. Transportation Research Record 1035, Transportation Research Board, Washington, D.C. [17] Steven Chien.; Paul Schonfeld. (2001): Optimal work zone lengths for four-lane highways. Journal of Transportation Engineering, 127(2). [18] Sun, D.; R. Benekohal,(2004): Analysis of Car Following Characteristics for Estimating Work Zone Safety, the 83rd Annual Conference of Transportation Research Board (TRB) of the National Research Council, No , CD-ROM Washington D.C. ISSN : Vol. 4 No.02 February