EFFECT ON COST OF ROAD CONSTRUCTION & MAINTENANCE DUE TO OVERLOADING

Transcription

1 EFFECT ON COST OF ROAD CONSTRUCTION & MAINTENANCE DUE TO OVERLOADING INTERNATIONAL CONFERENCE ON ASSESSING THE NEED FOR THE MANAGEMENT OF AXLE LOADS IN DEVEOPING COUNTRIES, COLOMBO, SRI LANKA JUNE 2006 Amal S. Kumarage, Professor of Civil Engineering, Transportation Engineering Division, Department of Civil Engineering, University of Moratuwa, Sri Lanka. Saman Bandara, Professor of Civil Engineering, Head, Department of Transport & Logistics Management, University of Moratuwa, Sri Lanka, Gunathileke Bandara, Deputy Director, Planning Division, Road Development Authority, Sri Lanka, 1

2 INTRODUCTION As a protective measure the Motor Traffic Act stipulates maximum gross and tare weights, axle loads, and dimensions. These limits are meant to ensure that roads last for the full design life with routine and periodic maintenance. The composition of the country s vehicle fleet changes over time, with new technology. Moreover when there is no effective regulation of axle loads transporters take financial advantage by overloading heavy goods vehicles. This is compounded by the fact that at the same time the volume of traffic keeps increasing. The road user charges designed to recover the cost of road provision, do not adequately demonstrate the economic cost of each vehicle in terms of the road damages due to axle overloading. The combined effect of these changes is that there is an increase in road damage measured by the increase in the annual total number of cumulative standard axles load on the road network. It has not been possible to ensure that road pavements at all times are structurally upgraded to keep pace with the increased total weights due to financial and other resources constraints. The present regulations under the Motor Traffic Act does not provide for a rational axle load for effective enforcement, and does not include provisions to control and punish for excessive axle loads. Much of Sri Lanka s roads and bridges were designed for lighter traffic and loads than what moves on them today. Roads and bridges in areas where conflict has prevented proper maintenance are particularly vulnerable to excessive loads. Given the recognised importance of the road network for Sri Lanka s development, the issue of an effective overload control has emerged as a strategic one. There is a need to assess various aspects of managing overloading with effective control and enforcement in the country, in order to identify possible constraints and in order to raise the awareness of what economic consequences are involved with this practice and identifying what needs to be done. The Road Development Authority (RDA) has a stated program for axle load testing on National Highways. There are no other agencies carrying out axle load surveys on roads. The only other agency carrying out vehicle weighing is the Department of Motor Vehicles. This is at time of registration of vehicle, where Tare of the vehicle (un laden weight) is recorded in the registration. Vehicles that are overweight according to the Motor Traffic Act are thereafter directed to the Road Development Authority for recommendation for registration under special permit. Where recommendation is not provided it is declined for the registration. CONTROLLED SURVEY A controlled 48 hour Axle Load survey was carried out with the assistance of Road Development Authority on 15 th and 16 th of February 2005 at 58 th km (Malsiripura) of Ambepussa- Kurunegala Trincomalee Road (A6) in order to supplement the data available with the RDA. 2

3 Selection of Vehicles for Weighing was carried out using sampling rates for the target vehicle categories. Midi buses and Light Lorries with 2 axle & 4 wheels were not weighted as their capacity was considered to be less than the allowable GVW according to the axle configuration. In calculating overloading, the allowable GVW for this analysis is taken from the limits imposed by the Gazette No 248 of However, since there is no Allowable GVW for 6 axle vehicle in this gazette, the GVW for 6 axle vehicles was taken from the gazette no 1270/33 dated Accordingly the survey results given in Table 1 and 2 show that there is a considerable overloading of vehicles. Two Axle trucks are showing 43% of vehicles being over loaded. This is a trend for all goods vehicles, with multi axle trucks showing even 57% vehicles overloaded. The amount of overloading also appears to be even as high as 49 ESA per vehicle. 3

4 Table 1: Axle load survey summary at the survey carried out at 58 km of Ambepussa-Kurunegala-Trincomalee road (Malsiripura) (Date of survey: 15th February 2005) Description A06 Location 58km Long Bus Light lorry 2A/4W Lorry 2A/ 6W 3 Axle Road Vehicle count vpd Surveyed No Vehicles with in Total legal limits ESA Over load vehicles surveyed 4 Axle No Total ESA Year Total surveyed % surveyed 23% 0% 22% 51% 69% 84% 50% 70% Average ESA of vehicles with in legal limit % Overloaded vehicles Average ESA of overloaded vehicles 2% 0% 43% 52% 26% 50% 0% 57% Average ESA for all vehicles Axle Tractor & Trailer 6 Axle Midi Bus Cars 3W Motor Cycle Total 4

5 Table 2: Analysis of Overloading Description Long Bus Light lorry 2A/4W Lorry 2A/ 6W 3 Axle 4 Axle 5 Axle Tractor & Trailer 6 Axle Allowable GVW in Tons Vehicles overloaded by less than 25 %GVW Vehicles overloaded by less than 50 % but exceeding 25% GVW Vehicles overloaded by less than 75 % but exceeding 50% GVW Vehicles overloaded by less than 100 % but exceeding 75% GVW Vehicles overloaded by more than 100 % GVW Nos Total ESA Avg. ESA % from Total 0.38% 5.41% 4.17% Nos Total ESA Avg. ESA % from Total 3.21% 10.83% 2.22% Nos Total ESA Avg. ESA % from Total 0.19% 0.97% 5.83% 6.67% 32.56% 40.00% Nos Total ESA Avg. ESA % from Total 4.17% 6.67% 9.30% Nos 2 1 Total ESA Avg. ESA % from Total 1.67% 2.22% 5

6 There are several observations that can be derived from this survey result. 1 All loaded 6 axle commercial trucks that were weighed, were overloaded and 40 % of them were overloaded by more than 50% of the allowable GVW (i.e. a load of 150% of GVW). The average ESA value for these 6 axle loaded vehicles is around 49.4 ESAs 2 Nearly 10 % of the 5 axle commercial trucks are overloaded by more than 75% of the allowable GVW and their ESA value is around 51 ESAs. Nearly 33% of these 5 axle trucks are overloaded by more than 50% of their allowable GVW. Average ESA for these vehicles are around 31 ESAs 3 Around 2% of 3 axle and 4 axle trucks are overloaded more than 100 % of their allowable GVW. ESA value for these vehicles are 58.3 ESA and 66.4 ESA for 3 axle trucks and 4 axle trucks respectively. 4 Considerable percentage of 3 axle and 4 axle trucks are overloaded more than 75 % of their allowable GVW EFFECT ON COST OF ROAD CONSTRUCTION AND MAINTENANCE DUE TO OVERLOADING Road pavements are designed to carry vehicles loaded within allowable Gross Vehicles Weight (GVW). According to the design procedure, the pavement thickness is designed to accommodate a total number of axle movements by the end of the design life. This number of axle movements is referred to as the Cumulative Equivalent Standard Axles which demotes the serviceability of the pavement during its design life. Usually the Cumulative ESAs are calculated as the estimated ESAs for a design period such as 15 years. It is necessary that on completion of the 15 years or more exactly the cumulative passes of ESA, the pavement road has to be overlaid or reconstructed depending of the residual strength of the pavement. Loading Scenarios In order to estimate the cost of overloading, the reduction in life cycle cost when an overloaded vehicle travels a road section of 1 km has been calculated. This has been done for the Ambepussa- Kurunegala Trincomalee road (A6) where the control survey was carried out. In order to estimate costs, the following different overloading scenarios have been taken in to consideration. Scenario 1: Vehicles will carry only the allowable GVW and there will be no overloading. Scenario 2: All Loaded vehicles will carry loads that are 25 % in excess of the GVW Scenario 3: All Loaded vehicles will carry loads that are 50% in excess of the GVW Scenario 4: The vehicles will carry the present observed levels of overloading ESA values for commercial vehicles for these scenario are calculated and given in the Table 3 below 6

7 ESA Value for Vehicles Type Long Bus Light lorry 2A/4w Table 3: ESA Value for Vehicles Lorry 2A/6w 3 axle commerci al 4 axle commer cial 5 axle commer cial Tractor and trailer 6 axle commer cial GVW Loading scenario ESA Scenario Scenario Scenario Scenario Empty During the survey it was observed that there is no overloading on the vehicle types- Long buses, Light lorry and Tractor & trailer. Accordingly the average ESA value calculated from the axle load survey has been used for all the different scenarios for these vehicles. Cumulative number of ESA values was calculated with the following assumptions 1 vehicle growth rate 4 % 2 No change of ESA value for vehicle long buses, light Lorries and tractor & trailer and their ESA as calculated from the axle load survey. 3 Portion of empty vehicles remain same as observed at the survey 4 Analysis period is 15 years starting from year 2005 Calculation of ESA for the above scenarios is summarized in below Table 4. Table 4: Cumulative ESA for 15 Year Design Life Scenario Description CNESA 1 for 15 years in millions Scenario 1 All Loaded vehicles will carry only the allowable GVW Scenario 2 All Loaded vehicles will be overloaded by 25% of GVW Scenario 3 All Loaded vehicles will be overloaded by 50 % of GVW Scenario 4 Vehicles will continue to be overloaded as at present Design Options Two design options were considered for Scenario 1 and Scenario 4 assuming that the present road pavement has strength to give Benkelman Beam deflection of less than 0.77mm for overlay design as used by Road Development Authority. 1 CNESA - Cumulative Number of Equivalent Standard Axles 7

8 Accordingly overlay thickness are as follows: For scenario 1 to accommodate CNESA of millions is 120mm For scenario4 to accommodate CNESA of millions is 200mm Cost of these overlay works are calculated and given below Basic cost Item Unit Unit cost (Rs.) A C with out transport for raw aggregate Rs./M tons Transport of aggregate Rs. /cum/km Transport of AC to site Rs./ M tons 7.05 Laying and Compaction Rs./M tons Tack coat.75 Lt/Sqm Rs Transport of emulsion Rs./100Lt/Km 1.55 Overlay Design Scenario 1 Scenario 2 Road width m Length of the Road section m Thickness of overlay mm Cost of construction Item Amount( Rs) Scenario 1 Scenario 2 4,827, ,045, Cost of AC transport 50km to site 888, ,480, Cost of transport for aggregate for AC 20 km to site 202, , Laying and Compaction 1,261, ,101, Tack coat.75 Lt/Sqm 108, , Transport of Emulsion for tack coat 50km 4, , Total 7,292, ,078, Correction of ruts and depressions 50mm 2,403, ,403, sub Total 9,695, ,481, % contingencies 969, ,448, Cost of construction works 10,664, ,929, Consultancy 10 % 1,066, ,592, Add for Tax,overheads and profit 4,692, ,009, Cost of the project per km 16,424, ,532, TOTAL Say 16,424, ,532, Above calculated costs were taken as the overlay (capital) cost with the maintenance cost of the surface for a year was taken as 2 % of the overlay cost. Comparison of life cost Life Cost calculation was as follows: Scenario 1: Overlay is design to accommodate CNESA and overlay will be at the beginning of the year and maintenance of the surface will be carried out during the balance period. 8

9 Scenario 2: Overlay will be carried out as for the scenario 1 and new overlay will be carried out when ever CNESA exceeds the design value. Accordingly 120mm thick overlay will be carried out at the beginning and subsequent overlay will be carried out when ever CNESA exceed million easels. The overlays will be at 5 th year (2009), 9 th year (2013) and 13 th year (2017) Scenario 3: Overlay is same as scenario 2 but subsequent overlays will be at 4 th (2008), 7 th (2011), 10 th (2014), 12 th (2016), 14 th (2018) and 16 th (2020) year. Scenario 4: Overlay will be carried out to accommodate present overloading levels. Overlay thickness will be design to CNESA of millions easels for the 15 year life span and that will be carried out at the beginning of the year. 2% of the overlay cost for a year will be spent for the maintenance in the balance period. The costs were converted to present value by a discount rate of 10 %. 9

10 Year Load carrying vehicles loaded only to GVW Table 5 : Comparison of Life cycle cost for difference overloading scenarios Cost of overlay and maintenance (Rs. Millions) 25 % over GVW Overloading 50 % over GVW Overloading Pavement design to accommodate present overloading load situation Yearly cost Discounted cost Yearly cost Discounted cost Yearly cost Discounted cost Yearly cost Discounted cost Total Rs mn CNESA Cost per ESA km (Rs)

11 This clearly shows that the life cycle cost per ESA km for road haulage of an typical truck representing the current mix of vehicels ranges from Rs 0.45 to Rs 1.01 for different design standards. The optimum cost is when road designs are undertaken assuming 50% overloading. As indicated in Table 5, the cost of providing roads decreases with the increase of overloading level, provided however that the pavement is designed for increased levels of loading. However this needs to be further studied to arrive at a final determination of the optimum cost of loading levels for each type of vehicle. The following calculations were carried out to identify the most suitable vehicle type for the transport of cumulative load in each scenario of over loading. In this analysis each vehicle type has been recognized by the respective ESA of that vehicle type. Thereafter the cumulative design life ESA (CNESA) for each vehicle type is given in the Table 6. The vehicles which produced the lowest ESAs at each loading scenario in transporting of the same load are the suitable vehicle for the transportation of the load. If it is possible to use the most suitable vehicle for the transportation it will extend the life of the pavement design for a particular road. Using the calculated values, Life extension factor for all vehicles on each of the loading scenario were calculated as given below: CNESA at all vehicles in the traffic stream Life Extension Factor = CNESA when one type of vehicle is taking the load According to Table 4, the 4 axle commercial vehicle is the most suitable vehicle for the transportation of loads at GVW and 25% overloading level (Scenarios 1 and 2). At 50% overloading (scenario 3) level the 5-axle vehicle is the most suitable vehicle for the transportation of the loading at that time. 11

12 Loading Scenario Table 6: Life Extension Factor for Optimum ESA at Different Loading Levels only use of vehicle 12 Discounted cost (Rs. Millions) CNESA with all vehicles (million esa) Cumulative load in Tons CNESA Life extension factor CNESA Life extension factor CNESA Life extension factor CNESA Life extension factor CNESA Life extension factor Lorry 2A/ 6W 3 Axle 4 Axle 5 Axle 6 Axle Load carrying vehicles loaded only to GVW 25 % over GVW Overloading 50 % over GVW Overloading Pavement design to accommodate present overloading situation

13 Road User Costs Collected The most appropriate vehicle type however also depends on the revenue collected for each vehicle type. Thus this section follows the revenue collection processes for each vehicle type. The total road user costs collected from different sources without adjusting for the fuel subsidy are tabulated in the following table. All vehicles are assumed to have an average time lifespan of 15 years, and have an operating span of 400,000 kms. The road user cost recovered per ESA km operated based on average ESA per vehicle is shown below. Table 7 : Revenue Collection for Different Vehicle Types Vehicle Type Total Recovery (Rs over 15 years) Average ESA per vehicle Recovery Rs per ESA km Truck 2A/4W 784, Truck 3 Axle 1,037, Truck Articulated 1,454, Large Bus 534, It is seen that that the highest collection is from the 2Axle trucks, while the larger trucks pay about 30% less. Buses on the other hand pay several times more. However with the present diesel subsidy ranging from Rs 3 to even as high as Rs 12 per litre, then the cost per ESA would range between Rs 1 and Rs 4. Thus this would actually result in a net subsidy from all road haulage vehicles. CONCLUSIONS 1 The present legislation pertaining to vehicle weights and dimensions in Sri Lanka is from The amendment in 2003 appears to incorporate some steps in the correct direction. However, the load levels that have been specified have not been computed after research or study. 2 The legislation on vehicle weights has not been based on an acceptable study, comparison of limits in other countries or the extent of road damage and costs of provision of roads. 3 The present cost recovery from road haulage vehicles also seems inconsistent and does not appear to recover the true cost. Neither does it recover in the same proportion between different vehicle types. The diesel subsidy appears to be a net subsidy for all types of road haulage. 4 The surveys show that overloading is significant and frequent. This occurs in all road haulage vehicles. The survey conducted for the study shows that: a. All loaded 6 axle commercial trucks that were weighed, were overloaded and 40 % of them were overloaded by more than 50% of the allowable GVW (i.e. a load of 150% of GVW). b. Nearly 33% of these 5 axle trucks were overloaded by more than 50% of their allowable GVW. 13

14 c. Around 2% of 3 axle and 4 axle trucks were overloaded more than 100 % of their allowable GVW. d. Considerable percentage of 3 axle and 4 axle trucks were overloaded more than 75 % of their allowable GVW. 5 The general attitude of State Agencies on recovery of actual road user costs and the desire to enforce limitation on vehicle weights has been very poor. To begin with there has been very little discussion or public debate on the need to enforce vehicle weights. Secondly, there has been no awareness of the need to price use of road space. The traditional approach that the government has to finance all road provision and the maintenance of them continues to prevail. Furthermore the attitude that anything and anyone should be allowed to use the roads with as few fetters as possible is also a general public attitude. 6 The life cycle cost for an ESA km ranges between Rs 0.45 to Rs 1.01 depending on the loading levels adopted at time of design. At current design standards, the 4 axle commercial vehicle is the most suitable vehicle for the transportation of loads up to 25% overloading level. However, beyond that the 5-axle vehicle is has the lowest life cycle cost per ESA km. 7 It has also been shown that the optimum life cycle cost for the road design will be realised if it is assumed that in general there would be 50% overloading. Thus if indeed the roads are designed for higher loads in the future, then there would be a net reduction in life cycle cost per ESA km. 8 However, even if new or rehabilitated roads are thus designed the fact that the other sections of the road network which is badly deteriorated cannot take up overloading without causing severe failure is a limiting factor. The exact calculation of this scenario has not been carried out to date. Since this is beyond the scope of this study it may be recommended as a future activity. 9 The road provision cost recovered from goods vehicles through taxes ranges between 28 cts and 43 cts per km. of this the highest collection is from the 2 axle trucks, while the larger trucks pay about 30% less.. This is below the average costs of between 45 cts and Rs 1.01 stated earlier. In addition, the diesel fuel subsidy also contributes a further Rs 1 per ESA km (approximately). Thus all forms of road freight haulage vehicles are presently receiving a net subsidy. 10 Buses on the other hand have a cost recovery of Rs 1.91 per km, via taxes and fees. In this case there is a revenue surplus with respect to road user charges. However, with the diesel subsidy buses receive a net subsidy. 14