- Email: [email protected]
Climbing Lane Level of Service Estimation in Spain
Available online at www.sciencedirect.com
ScienceDirect Transportation Research Procedia 18 (2016) 366 – 373
XII Conference on Transport Engineering, CIT 2016, 7-9 June 2016, Valencia, Spain
Climbing Lane Level of Service Estimation in Spain Víctor Gabriel Valencia Alaixa*, Alfredo Garcíab a
Universidad Nacional de Colombia, Calle 65 #78-28, Medellín, 050034, Colombia Universitat Politècnica de València, Camino de Vera, s/n., 46022, Valencia, Spain
b
Abstract A road in Spain was monitored with cameras with the objective of calibrating the TWOPAS model, which was successfully achieved with the information gathered. The model was also applied for estimating its Level of service, with and without a climbing lane, and for comparing the results with those obtained with the Highway Capacity Manual (HCM) procedure. The basic indicators were Percent Time Spent Following (PTSF) and Average Travel Speed (ATS). As a result, it is concluded that the two procedures show improvements on the climbing lane applicable on the field. However, changes are recommended to improve the estimation © Published Elsevier This is an open access article under the CC BY-NC-ND license © 2016 2016The TheAuthors. Authors. ElsevierbyB.V. All B.V. rights reserved. Peer review under responsibility of the organizing committee of CIT 2016 (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of CIT 2016 Keywords: Climbing lane; Two-lane Rural Road; TWOPAS; IHSDM; Level of Service.
1. Introduction Circulation quality in two lane roads is closely related to the level of attention given to passing, which, if neglected, can lead to slow speeds, long delays, platooning, etc. An alternative for mitigating such issues is the creation of climbing lanes for trucks. This paper intends to provide insight into the performance of climbing lanes for trucks by applying and comparing methodologies to estimate the Level of service (LOS) of a two lane road with and without a climbing lane.
* Corresponding author. Tel.: +57-4-4255165; fax: +57-4-4255152. E-mail address: [email protected]
2352-1465 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of CIT 2016 doi:10.1016/j.trpro.2016.12.048
Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
2. State of the art The implementation of auxiliary lanes on a two lane road encompasses different options, among which are passing and climbing lanes. Khan et al. (1991) studied how to improve passing and concluded that a methodology for evaluation must consider operational improvements for a considerable length of the road. They defined a methodology to estimate the effect of passing lanes on level of service, and selected percentage of vehicles per group and ATS from the different indicators under consideration. The operational evaluation of the chosen scenarios was carried out with simulation models. Moreover, Messer (1983) found out that the PTSF can be estimated by measuring the percentage of vehicles in circulation that form platoons with headways of less than five seconds. May (1991) used four-second headways for measuring PTSF, while TWOPAS, which is the core of the Traffic Analysis Module (TAM) within the Interactive Highway Safety Design Model (IHSDM) suggests three seconds, FHWA (2013). Furthermore, Khan et al. (1991) used simulations to develop guidelines to determine the proper length of a passing lane and its effective distance after it ends. Harwood and St. John (1986) concluded that the reduction of platooning percentage may persist over an effective distance of 8 to 12.8 km, depending on the length of the passing lane, traffic flow, traffic composition, and availability of opportunities for passing. Morrall and Thomson (1990) determined that PTSF and opportunity for passing are not only more significant in terms of perceived Level of service for drivers, but may also be used to evaluate the effectiveness of passing lanes. May (1991) observed traffic on five California roads with indicators such as speed and PTSF. Operational benefits were found using PTSF, traffic percentage with two-second headways, and single vehicles. The results showed significant improvements, especially on mountain areas and long lanes. Al-Kaisy and Freedman (2010) carried out measurements on passing lanes in two Montana sites and analyzed the improvements in places located before, on, and after the auxiliary lane using PTSF, ATS, and other indicators such as percentage of followers, density of followers, and the relation between speed and free flow speed (ATS/FFS). Improvements were indeed noticed throughout the effective length in magnitudes corresponding with those indicated in the HCM, TRB (2010). Freedman and Al-Kaisy (2013) monitored platooning and passing maneuvers on a passing lane on U.S. road 287 and measured the division in volume, percentage of followers, and density of followers per lane. This showed that passing takes place within the first half mile of the passing lane, which may suggest a new criterion for optimal length in auxiliary lanes. Regarding the design of passing lanes, Morrall and Thomson (1990) capitalized on the experience obtained through the study of experimental lanes on the Trans-Canada highway and established new criteria for defining locations and evaluating options for passing lanes. In relation to climbing lanes, Morrall and Thomson (1990) determined that these can be longer on steep and long grades than what is recommended for passing lanes in normal conditions due to the great difference in speed between cars and trucks. In order to evaluate speed reduction, designers recommend the use of a typical truck with a representative weight/power ratio as reference, Khan et al. (1990). Valencia, Bedoya, and Osorno (1996) measured the net weight/power ratio of heavy vehicles on Colombian roads based on dynamic equilibrium equations on ascending grades and concluded that their mean weighted value is 157 kg/CV, which is higher than those specified in the auxiliary lane warrants such as HCM. The HCM, TRB (2010) suggests a methodology to estimate the operational effect of a passing or climbing lane at a directional section of a two-lane road. It assumes that the effect of a passing lane on PTSF is that it is reduced throughout the auxiliary lane and it slowly increases after it ends, approaching levels of a road with no passing lane. According to the HCM, TRB (2010), such effective length is also reflected on the ATS behavior. The steps to follow are: x Carry out an operational analysis on the road without passing lane. x Divide the section into regions. ○ Lu = Length before passing lane.
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○ Lpl = Passing lane length. ○ Lde = Effective length. ○ Ld = Length after effective length Lde.
x Determine PTSF for the entire road section affected by passing lane, as in Equation (1):
(1)
PTSFpl = PTSF for the road section affected by the passing lane (decimal). fpl,PTSF = Correction factor due to effect of passing lane on PTSF. The PTSF value in the passing lane is between 0.58 and 0.62 of PTSF value in the previous region with length Lu. x Determine ATS for the entire road section affected by the passing lane, as in Equation (2):
(2)
ATSpl = ATS for the road section affected by the passing lane (decimal). fpl,ATS = Correction factor due to effect of passing lane on ATS. The ATS value in the passing lane is between 8 % and 11 % over the ATS value in the previous region with length Lu. x Determine level of service according to Table 1. Table 1. Level of Service for two lane roads considering cars, TRB (2010). LOS Class I Highways Class II Highways
A B C D E
ATS (mi/h) >55 >50–55 >45–50 >40–45 ≤40
PTSF (%) ≤35 >35–50 >50–65 >65–80 >80
PTSF (%) ≤40 >40–55 >55–70 >70–85 >85
Class III Highways PFFS (%) >91.7 >83.3–91.7 >75.0–83.3 >66.7–75.0 ≤66.7
The operational analysis of the effect of an climbing lane in a two lane road is carried out using the same procedure described for passing lanes, save for three important differences: x The correction factors due the effect of a climbing lane are different. x The analysis without a climbing lane is carried out using the normal procedure for a road without climbing lanes, but for a specific upgrade. x Lengths Lu and Ld are set at zero. The HCM, TRB (2010) and the Green Book, AASHTO (2011), justify the implementation of a climbing lane under the following conditions:
Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
x Traffic flow on the upgrade exceeds 200 veh/h. x Truck flow on the ascending grade exceeds 20 trucks/h. x And one of the following: ○ There is a speed reduction of 15 km/h or more for the usual 120 kg/kW (200 lb/hp o 90 kg/CV) truck. ○ There is an E or F level of service on the grade. ○ There is a reduction of two or more levels of service when driving between access and grade. According to the normative for the tracing of two lane roads in Spain, Norma 3.1-IC. Trazado (Orden FOM/273/2016), Ministerio de Fomento (2016), the implementation of an additional lane on a ramp on a two-lane road considers the same criteria as the Green Book, AASHTO (2011) and HCM, which require the fulfilment of three simultaneous conditions. The TWOPAS was developed by the Midwest Research Institute for the Federal Highway Administration, FHWA (2013); it microscopically simulates traffic operation in two lane roads, with or without auxiliary lanes, based on user specific traffic and road features. According to a study carried out by the NCHRP (1998), the TWOPAS was used for developing the HCM chapter on capacity and levels of service on two-lane roads, considering the omitted values found in the configuration file of TAM (module from IHSDM) as part of the operative capacity of the number of motor vehicles in the U.S.
3. Objectives 3.1. General To calibrate the TWOPAS and use it in the evaluation of a climbing lane in Spain to determine the level of service and compare it with the HCM methodology.
3.2. Specific x x x x
Observe traffic operations on a two lane road with a climbing lane in Spain. Calibrate the TWOPAS model. Apply the TWOPAS to operationally evaluate the road and climbing lane. Determine and compare the level of service with the HCM methodology and the simulation.
4. Methodology 4.1. Experimental section The CV13 is a conventional road in the Comunidad Valenciana (Spain) with a length of 16.5 km which contains the first traveled way of a future freeway; it operates as a two lane road (P.K. 2+500 at 16+500), Generalitat Valenciana (2010) as shown in Figure 1. Roadway made of two lanes of 3.50 m with increasing shoulders of 1.50 m and 2.50 m to the right and left of the road in direction to P.K. increasing, respectively, with a projected capacity of 50,000 veh/day. The longitudinal profile has grades of around 5 %, which allows for a climbing lane of 2,630 m. The road counts with an Intelligent Transportation System (ITS) for monitoring and control composed of 14 cameras that cover 100 % of the road, which has been useful in the gathering of traffic information. The road was designed for speeds of up to 100 km/h and a minimum radius of 450 m. The measured volume for direction P.K. increasing is 184 veh/h and 191 veh/h in the opposite direction.
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Figure 1. CV13 Road scheme
Every time a vehicle passed, the cameras recorded and identified it according to its type and direction to measure, among other things: x x x x
ATS PTSF Vehicle volume and composition Desired speed
4.2. TWOPAS Calibration The measurement of traffic variables is used for the analysis of current road behavior and the estimation of operational indicator values to calibrate the TWOPAS. This paper used the methodology applied by Valencia (2016) for calibrating the TWOPAS in Colombia. 4.3. Level of service estimation according to HCM The level of service was calculated with the 2010 HCM method for road CV13 with and without climbing lane. 4.4. Application of TWOPAS calibrated in CV13 The TWOPAS calibrated in road CV13 was applied to establish the PTSF and ATS with and without climbing lane to be able to calculate its LOS. 5. Results 5.1. Calibration The TWOPAS was configured through TAM modifying certain parameters in the model, among which stand out the operational features of vehicles and drivers’ desired speed. The weight/power ratio of trucks for calibration was estimated with the procedure applied by Valencia, Bedoya, and Osorno (1996), measuring sustained speed on a ramp of 4.7 %. See Table 2 for results.
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Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
Table 2. Sustained speed and weight/power ratio of trucks in CV13 (Valencia, 2016). Type of truck for TWOPAS Sustained speed Standard deviation Estimated weight/power ratio (km/h) (km/h) (kg/CV) 1 42.5 9.1 85.7 2 41.6 Not available 88.0 3 4
40.4 45.8
3.4 13.7
90.6 82.7
The TWOPAS was applied in road CV13 between P.K. 8+264.000 and P.K.16+333.400, and to assess the calibration, the approximation ratio between values of simulated operational indicators and their corresponding measured values were analyzed. See results in Table 3. Values in the approximation ratio column correspond to the excess or defect percentage that the value of the simulated indicator has in relation to the one measured on the field. Once the average of the absolute values of the approximation ratio is satisfactory, then the TWOPAS can be considered calibrated. Table 3. Approximation ratio between values measured in road CV13 and simulated with TWOPAS. Operational Measured in CV13 Simulated with TWOPAS (TAM) indicator Direction 1 (PKs Direction 2 (PKs Direction 1 (PKs Direction 2 (PKs increasing) decreasing) increasing) decreasing) Flow rate from 181.8 178.7 162 180 simulation (veh/h) PTSF (%) 36 39 48 44 ATS (km/h) 93.1 81.9 87.2 65.2 Trip time (min/veh) 5.17 6.1 5.5 7.4 Number of passes Not available Not available 47 113 Distance traveled 1421.19 1452.55 1304 1446.4 (km) Total travel time 15.1 19 14.9 22.2 (veh-h) AVERAGE APPROXIMATION RATIO MEAN OF THE ABSOLUT VALUES OF THE APPROXIMATION RATIO
Approximation ratio (%) Direction 1 (PKs increasing) -10.9
Direction 2 (PKs decreasing) 0.7
33.3 -6.3 6.4 Not available -8.2
12.8 -20.4 21.3 Not available -0.4
-1.3
16.8
2.2 11.1
5.1 12.1
5.2. Level of service with HCM The procedure was applied to determine the road’s LOS with and without a climbing lane. In the climbing lane case, only the road section with a climbing lane of length (L pl) of 2,630 m was considered. Sections before and after the climbing lane (Lu, Lde y Ld) were not taken into account. The following characteristics were considered: x x x x x x x
Directional distribution: 52 % on ascent, and 48 % on descent. Directional distribution of trucks: 38 % on ascent, and 36 % on descent. Lane width of 3.50 m. FHP = 0.90 No passing zones in both directions = 62.8% Access number per mile = 0 Basic free flow speed (BFFS): 106.2 km/h on ascent, and 118.8 km/h on descent.
Table 4 shows results for situations with and without climbing lane that reflect an improvement on traffic circulation quality in relation with the road without a climbing lane.
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Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373 Table 4. Level of service with and without a climbing lane according to HCM procedure. Section Indicator Level of service Entire road ATSd = 97.2 km/h = 60.8 mi/h A PTSFd = 51 % C Climbing lane ATSpl = 111 km/h = 69.4 mi/h A PTSFpl = 10 % A
5.3. Level of service with calibrated TWOPAS Traffic simulation in CV13 with situations with and without a climbing lane and calibrated TWOPAS rendered the PTSF and ATS results displayed on Table 5 with their corresponding LOS. Table 5. Level of Service with and without climbing lane as per simulation with calibrated TWOPAS. Section Indicator Level of service Entire road ATS = 65.5 km/h = 40.9 mi/h D PTSF = 40 B Climbing lane ATS = 67.8 km/h = 42.4 mi/h D PTSF =20 A
6. Conclusions The weight/power ratio of trucks had a mean value of 88 kg/CV that practically corresponds to the typical truck considered in the Green Book, 120 kg/KW (90 kg/CV), which justifies the implementation of climbing lanes and has been adopted by Spanish policy. This serves as evidence of the correspondence with real-world situations observed on the road. The acceptable approximation ratio obtained between the indicators simulated by TWOPAS and those measured on road CV13 allow us to conclude that the model is calibrated for the CV13, effectively validating itself as traffic analysis tool, as it was used for this paper. According to the calibration results obtained, it could be said that the TWOPAS calibration can be improved through additional steps such as adding more detailed measures of different indicators, e.g., geometrical delays, traffic delays, number of passing, as well as others that are subject to future studies. The comparison of the resulting levels of service rendered by the two procedures used, HCM and simulation, show that both display improvements in traffic operations, with the climbing lane being more susceptible with PTSF and revealing changes between one and two LOS but remaining stable with ATS. Notwithstanding the TWOPAS calibration, which could indicate that the indicator results represent traffic behavior in road CV13, the results obtained by the HCM procedure with the same typical truck weight/power ratio of 90 kg/CV, are different. The HCM overestimates the ATS and the PTSF for the entire road by 32.6 % and 21.5 %, respectively; however, with a climbing lane, the HCM overestimates the ATS by 38.9 % and underestimates the PTSF by 100 %. Thus, it is concluded that it is necessary to either improve the TWOPAS calibration or adjust the HCM procedure to Spanish conditions. Furthermore, the TWOPAS should be calibrated and validated for the climbing lane scenario, as this was not done in the present study. According to the TWOPAS CV13 simulation results, especially in the evaluation of the climbing lane, the unusual location of the climbing lane at the end of the ramp stands out, as the PTSF and ATS results reveal greater possible benefits if the climbing lane started closer to the beginning of the ramp. The most operationally convenient location
Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
can be determined through a series of applications of a calibrated TWOPAS, as recommended by Valencia and García in 2010. References AASHTO, 2011. A Policy on Geometric Design of Highways and Streets, fifth edition. Washington, D. C.: AASHTO. Washington, D.C. USA. xliv + 1006 pp FHWA, 2013. Traffic Analysis Module Engineer's Manual. Federal Highway Administration. Office of Safety Research and Development, TurnerFairbank Highway Research Center, McLean, VA. September. Freedman, Z., Al-Kaisy, A. 2013. Investigation of performance and lane utilization within a passing lane on a two lane rural highway. International Journal for Traffic and Transport Engineering, 2013, 3(3): 279 – 290. Generalitat Valenciana, 2010. Puesta en servicio de la CV13 entre la CV10 (Benlloch) y la AP7 (Torreblanca). Conselleria D´Infraestructures I Transport. Valencia, España. Harwood, D. W., St. John, A. D., 1986. Operational effectiveness of passing lanes on two-lane highways. Report Nº FHWA/RD-86/196. Federal Highway Administration. April. Al-Kaisy, A, Freedman, Z. 2010. Empirical Examination of Passing Lane Operational Benefits on Rural Two Lane Highways. Journal of the Transportation Research Forum, Vol. 49, No. 3 (Fall 2010), pp. 53-68. Khan, A. M. et al., 1990. Heavy Vehicle Performance on Grade and Climbing Lane Criteria. Research and Development Branch, Ministry of Transportation. Ontario, Canada. November, pp. x + 78. Khan, A. M. et al., 1991. Cost-effectiveness of Passing Lanes: Safety, Level of Service, and Cost Factors. Research and Development Branch, Ministry of Transportation. Ontario, Canada. September, pp. xi + 124. May, A. D., 1991. Traffic Performance and Design of Passing Lanes. Transportation Research Record 1303, TRB, National Research Council, Washington, D. C., pp. 63-73. Messer C. J., 1983. Two-lane, two-way highway capacity. Final report of NCHRP Project 3-28A. Transportation Research Board. Ministerio de Fomento de España, 2016. Norma 3.1-IC. Trazado (Orden FOM/273/2016 de 19 de febrero de 2016). Internet search: http://www.fomento.gob.es/MFOM/LANG_CASTELLANO/DIRECCIONES_GENERALES/CARRETERAS/NORMATIVA_TECNICA/T RAZADO/. Morrall, J., Thomson, W., 1990. Planning and Design of Passing Lanes for the Trans-Canada Highways in Yoho National Park. Canada Journal of Civil Engineering, Vol. 17, Nº 1. Canada, February, pp. 79-86. NCHRP, 1998. Capacity and quality of service of two-lane highways. NCHRP PROJECT 3-55(3). Task 6, Enhance, calibrate, and validate the selected simulation model. TWOPAS model improvements. Transportation Research Board, 2010. Highway Capacity Manual. HCM 2010. Washington, D. C.: Transportation Research Board. USA. Valencia, V. G., Bedoya, V. E., Osorno, M. E., 1996. Relación Peso/Potencia de Vehículos Pesados en Colombia. Memorias del IX Congreso Panamericano de Ingeniería de Tránsito y Transporte. December 6. La Habana (Cuba). Valencia, V., García, A., 2010. Procedures to Facilitate Passing on Conventional Highways by Means of Simulation, Proceedings of 4th International Symposium on Highway Geometric Design. Valencia (Spain). June 1 to 5. Valencia Alaix, V. G., 2016. Elaboración de procedimientos para facilitar el adelantamiento en carreteras convencionales aplicando simulación [Doctoral tesis unpublished]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/62413.
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ScienceDirect Transportation Research Procedia 18 (2016) 366 – 373
XII Conference on Transport Engineering, CIT 2016, 7-9 June 2016, Valencia, Spain
Climbing Lane Level of Service Estimation in Spain Víctor Gabriel Valencia Alaixa*, Alfredo Garcíab a
Universidad Nacional de Colombia, Calle 65 #78-28, Medellín, 050034, Colombia Universitat Politècnica de València, Camino de Vera, s/n., 46022, Valencia, Spain
b
Abstract A road in Spain was monitored with cameras with the objective of calibrating the TWOPAS model, which was successfully achieved with the information gathered. The model was also applied for estimating its Level of service, with and without a climbing lane, and for comparing the results with those obtained with the Highway Capacity Manual (HCM) procedure. The basic indicators were Percent Time Spent Following (PTSF) and Average Travel Speed (ATS). As a result, it is concluded that the two procedures show improvements on the climbing lane applicable on the field. However, changes are recommended to improve the estimation © Published Elsevier This is an open access article under the CC BY-NC-ND license © 2016 2016The TheAuthors. Authors. ElsevierbyB.V. All B.V. rights reserved. Peer review under responsibility of the organizing committee of CIT 2016 (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of CIT 2016 Keywords: Climbing lane; Two-lane Rural Road; TWOPAS; IHSDM; Level of Service.
1. Introduction Circulation quality in two lane roads is closely related to the level of attention given to passing, which, if neglected, can lead to slow speeds, long delays, platooning, etc. An alternative for mitigating such issues is the creation of climbing lanes for trucks. This paper intends to provide insight into the performance of climbing lanes for trucks by applying and comparing methodologies to estimate the Level of service (LOS) of a two lane road with and without a climbing lane.
* Corresponding author. Tel.: +57-4-4255165; fax: +57-4-4255152. E-mail address: [email protected]
2352-1465 © 2016 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of CIT 2016 doi:10.1016/j.trpro.2016.12.048
Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
2. State of the art The implementation of auxiliary lanes on a two lane road encompasses different options, among which are passing and climbing lanes. Khan et al. (1991) studied how to improve passing and concluded that a methodology for evaluation must consider operational improvements for a considerable length of the road. They defined a methodology to estimate the effect of passing lanes on level of service, and selected percentage of vehicles per group and ATS from the different indicators under consideration. The operational evaluation of the chosen scenarios was carried out with simulation models. Moreover, Messer (1983) found out that the PTSF can be estimated by measuring the percentage of vehicles in circulation that form platoons with headways of less than five seconds. May (1991) used four-second headways for measuring PTSF, while TWOPAS, which is the core of the Traffic Analysis Module (TAM) within the Interactive Highway Safety Design Model (IHSDM) suggests three seconds, FHWA (2013). Furthermore, Khan et al. (1991) used simulations to develop guidelines to determine the proper length of a passing lane and its effective distance after it ends. Harwood and St. John (1986) concluded that the reduction of platooning percentage may persist over an effective distance of 8 to 12.8 km, depending on the length of the passing lane, traffic flow, traffic composition, and availability of opportunities for passing. Morrall and Thomson (1990) determined that PTSF and opportunity for passing are not only more significant in terms of perceived Level of service for drivers, but may also be used to evaluate the effectiveness of passing lanes. May (1991) observed traffic on five California roads with indicators such as speed and PTSF. Operational benefits were found using PTSF, traffic percentage with two-second headways, and single vehicles. The results showed significant improvements, especially on mountain areas and long lanes. Al-Kaisy and Freedman (2010) carried out measurements on passing lanes in two Montana sites and analyzed the improvements in places located before, on, and after the auxiliary lane using PTSF, ATS, and other indicators such as percentage of followers, density of followers, and the relation between speed and free flow speed (ATS/FFS). Improvements were indeed noticed throughout the effective length in magnitudes corresponding with those indicated in the HCM, TRB (2010). Freedman and Al-Kaisy (2013) monitored platooning and passing maneuvers on a passing lane on U.S. road 287 and measured the division in volume, percentage of followers, and density of followers per lane. This showed that passing takes place within the first half mile of the passing lane, which may suggest a new criterion for optimal length in auxiliary lanes. Regarding the design of passing lanes, Morrall and Thomson (1990) capitalized on the experience obtained through the study of experimental lanes on the Trans-Canada highway and established new criteria for defining locations and evaluating options for passing lanes. In relation to climbing lanes, Morrall and Thomson (1990) determined that these can be longer on steep and long grades than what is recommended for passing lanes in normal conditions due to the great difference in speed between cars and trucks. In order to evaluate speed reduction, designers recommend the use of a typical truck with a representative weight/power ratio as reference, Khan et al. (1990). Valencia, Bedoya, and Osorno (1996) measured the net weight/power ratio of heavy vehicles on Colombian roads based on dynamic equilibrium equations on ascending grades and concluded that their mean weighted value is 157 kg/CV, which is higher than those specified in the auxiliary lane warrants such as HCM. The HCM, TRB (2010) suggests a methodology to estimate the operational effect of a passing or climbing lane at a directional section of a two-lane road. It assumes that the effect of a passing lane on PTSF is that it is reduced throughout the auxiliary lane and it slowly increases after it ends, approaching levels of a road with no passing lane. According to the HCM, TRB (2010), such effective length is also reflected on the ATS behavior. The steps to follow are: x Carry out an operational analysis on the road without passing lane. x Divide the section into regions. ○ Lu = Length before passing lane.
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○ Lpl = Passing lane length. ○ Lde = Effective length. ○ Ld = Length after effective length Lde.
x Determine PTSF for the entire road section affected by passing lane, as in Equation (1):
(1)
PTSFpl = PTSF for the road section affected by the passing lane (decimal). fpl,PTSF = Correction factor due to effect of passing lane on PTSF. The PTSF value in the passing lane is between 0.58 and 0.62 of PTSF value in the previous region with length Lu. x Determine ATS for the entire road section affected by the passing lane, as in Equation (2):
(2)
ATSpl = ATS for the road section affected by the passing lane (decimal). fpl,ATS = Correction factor due to effect of passing lane on ATS. The ATS value in the passing lane is between 8 % and 11 % over the ATS value in the previous region with length Lu. x Determine level of service according to Table 1. Table 1. Level of Service for two lane roads considering cars, TRB (2010). LOS Class I Highways Class II Highways
A B C D E
ATS (mi/h) >55 >50–55 >45–50 >40–45 ≤40
PTSF (%) ≤35 >35–50 >50–65 >65–80 >80
PTSF (%) ≤40 >40–55 >55–70 >70–85 >85
Class III Highways PFFS (%) >91.7 >83.3–91.7 >75.0–83.3 >66.7–75.0 ≤66.7
The operational analysis of the effect of an climbing lane in a two lane road is carried out using the same procedure described for passing lanes, save for three important differences: x The correction factors due the effect of a climbing lane are different. x The analysis without a climbing lane is carried out using the normal procedure for a road without climbing lanes, but for a specific upgrade. x Lengths Lu and Ld are set at zero. The HCM, TRB (2010) and the Green Book, AASHTO (2011), justify the implementation of a climbing lane under the following conditions:
Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373
x Traffic flow on the upgrade exceeds 200 veh/h. x Truck flow on the ascending grade exceeds 20 trucks/h. x And one of the following: ○ There is a speed reduction of 15 km/h or more for the usual 120 kg/kW (200 lb/hp o 90 kg/CV) truck. ○ There is an E or F level of service on the grade. ○ There is a reduction of two or more levels of service when driving between access and grade. According to the normative for the tracing of two lane roads in Spain, Norma 3.1-IC. Trazado (Orden FOM/273/2016), Ministerio de Fomento (2016), the implementation of an additional lane on a ramp on a two-lane road considers the same criteria as the Green Book, AASHTO (2011) and HCM, which require the fulfilment of three simultaneous conditions. The TWOPAS was developed by the Midwest Research Institute for the Federal Highway Administration, FHWA (2013); it microscopically simulates traffic operation in two lane roads, with or without auxiliary lanes, based on user specific traffic and road features. According to a study carried out by the NCHRP (1998), the TWOPAS was used for developing the HCM chapter on capacity and levels of service on two-lane roads, considering the omitted values found in the configuration file of TAM (module from IHSDM) as part of the operative capacity of the number of motor vehicles in the U.S.
3. Objectives 3.1. General To calibrate the TWOPAS and use it in the evaluation of a climbing lane in Spain to determine the level of service and compare it with the HCM methodology.
3.2. Specific x x x x
Observe traffic operations on a two lane road with a climbing lane in Spain. Calibrate the TWOPAS model. Apply the TWOPAS to operationally evaluate the road and climbing lane. Determine and compare the level of service with the HCM methodology and the simulation.
4. Methodology 4.1. Experimental section The CV13 is a conventional road in the Comunidad Valenciana (Spain) with a length of 16.5 km which contains the first traveled way of a future freeway; it operates as a two lane road (P.K. 2+500 at 16+500), Generalitat Valenciana (2010) as shown in Figure 1. Roadway made of two lanes of 3.50 m with increasing shoulders of 1.50 m and 2.50 m to the right and left of the road in direction to P.K. increasing, respectively, with a projected capacity of 50,000 veh/day. The longitudinal profile has grades of around 5 %, which allows for a climbing lane of 2,630 m. The road counts with an Intelligent Transportation System (ITS) for monitoring and control composed of 14 cameras that cover 100 % of the road, which has been useful in the gathering of traffic information. The road was designed for speeds of up to 100 km/h and a minimum radius of 450 m. The measured volume for direction P.K. increasing is 184 veh/h and 191 veh/h in the opposite direction.
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Figure 1. CV13 Road scheme
Every time a vehicle passed, the cameras recorded and identified it according to its type and direction to measure, among other things: x x x x
ATS PTSF Vehicle volume and composition Desired speed
4.2. TWOPAS Calibration The measurement of traffic variables is used for the analysis of current road behavior and the estimation of operational indicator values to calibrate the TWOPAS. This paper used the methodology applied by Valencia (2016) for calibrating the TWOPAS in Colombia. 4.3. Level of service estimation according to HCM The level of service was calculated with the 2010 HCM method for road CV13 with and without climbing lane. 4.4. Application of TWOPAS calibrated in CV13 The TWOPAS calibrated in road CV13 was applied to establish the PTSF and ATS with and without climbing lane to be able to calculate its LOS. 5. Results 5.1. Calibration The TWOPAS was configured through TAM modifying certain parameters in the model, among which stand out the operational features of vehicles and drivers’ desired speed. The weight/power ratio of trucks for calibration was estimated with the procedure applied by Valencia, Bedoya, and Osorno (1996), measuring sustained speed on a ramp of 4.7 %. See Table 2 for results.
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Table 2. Sustained speed and weight/power ratio of trucks in CV13 (Valencia, 2016). Type of truck for TWOPAS Sustained speed Standard deviation Estimated weight/power ratio (km/h) (km/h) (kg/CV) 1 42.5 9.1 85.7 2 41.6 Not available 88.0 3 4
40.4 45.8
3.4 13.7
90.6 82.7
The TWOPAS was applied in road CV13 between P.K. 8+264.000 and P.K.16+333.400, and to assess the calibration, the approximation ratio between values of simulated operational indicators and their corresponding measured values were analyzed. See results in Table 3. Values in the approximation ratio column correspond to the excess or defect percentage that the value of the simulated indicator has in relation to the one measured on the field. Once the average of the absolute values of the approximation ratio is satisfactory, then the TWOPAS can be considered calibrated. Table 3. Approximation ratio between values measured in road CV13 and simulated with TWOPAS. Operational Measured in CV13 Simulated with TWOPAS (TAM) indicator Direction 1 (PKs Direction 2 (PKs Direction 1 (PKs Direction 2 (PKs increasing) decreasing) increasing) decreasing) Flow rate from 181.8 178.7 162 180 simulation (veh/h) PTSF (%) 36 39 48 44 ATS (km/h) 93.1 81.9 87.2 65.2 Trip time (min/veh) 5.17 6.1 5.5 7.4 Number of passes Not available Not available 47 113 Distance traveled 1421.19 1452.55 1304 1446.4 (km) Total travel time 15.1 19 14.9 22.2 (veh-h) AVERAGE APPROXIMATION RATIO MEAN OF THE ABSOLUT VALUES OF THE APPROXIMATION RATIO
Approximation ratio (%) Direction 1 (PKs increasing) -10.9
Direction 2 (PKs decreasing) 0.7
33.3 -6.3 6.4 Not available -8.2
12.8 -20.4 21.3 Not available -0.4
-1.3
16.8
2.2 11.1
5.1 12.1
5.2. Level of service with HCM The procedure was applied to determine the road’s LOS with and without a climbing lane. In the climbing lane case, only the road section with a climbing lane of length (L pl) of 2,630 m was considered. Sections before and after the climbing lane (Lu, Lde y Ld) were not taken into account. The following characteristics were considered: x x x x x x x
Directional distribution: 52 % on ascent, and 48 % on descent. Directional distribution of trucks: 38 % on ascent, and 36 % on descent. Lane width of 3.50 m. FHP = 0.90 No passing zones in both directions = 62.8% Access number per mile = 0 Basic free flow speed (BFFS): 106.2 km/h on ascent, and 118.8 km/h on descent.
Table 4 shows results for situations with and without climbing lane that reflect an improvement on traffic circulation quality in relation with the road without a climbing lane.
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Víctor Gabriel Valencia Alaix and Alfredo García / Transportation Research Procedia 18 (2016) 366 – 373 Table 4. Level of service with and without a climbing lane according to HCM procedure. Section Indicator Level of service Entire road ATSd = 97.2 km/h = 60.8 mi/h A PTSFd = 51 % C Climbing lane ATSpl = 111 km/h = 69.4 mi/h A PTSFpl = 10 % A
5.3. Level of service with calibrated TWOPAS Traffic simulation in CV13 with situations with and without a climbing lane and calibrated TWOPAS rendered the PTSF and ATS results displayed on Table 5 with their corresponding LOS. Table 5. Level of Service with and without climbing lane as per simulation with calibrated TWOPAS. Section Indicator Level of service Entire road ATS = 65.5 km/h = 40.9 mi/h D PTSF = 40 B Climbing lane ATS = 67.8 km/h = 42.4 mi/h D PTSF =20 A
6. Conclusions The weight/power ratio of trucks had a mean value of 88 kg/CV that practically corresponds to the typical truck considered in the Green Book, 120 kg/KW (90 kg/CV), which justifies the implementation of climbing lanes and has been adopted by Spanish policy. This serves as evidence of the correspondence with real-world situations observed on the road. The acceptable approximation ratio obtained between the indicators simulated by TWOPAS and those measured on road CV13 allow us to conclude that the model is calibrated for the CV13, effectively validating itself as traffic analysis tool, as it was used for this paper. According to the calibration results obtained, it could be said that the TWOPAS calibration can be improved through additional steps such as adding more detailed measures of different indicators, e.g., geometrical delays, traffic delays, number of passing, as well as others that are subject to future studies. The comparison of the resulting levels of service rendered by the two procedures used, HCM and simulation, show that both display improvements in traffic operations, with the climbing lane being more susceptible with PTSF and revealing changes between one and two LOS but remaining stable with ATS. Notwithstanding the TWOPAS calibration, which could indicate that the indicator results represent traffic behavior in road CV13, the results obtained by the HCM procedure with the same typical truck weight/power ratio of 90 kg/CV, are different. The HCM overestimates the ATS and the PTSF for the entire road by 32.6 % and 21.5 %, respectively; however, with a climbing lane, the HCM overestimates the ATS by 38.9 % and underestimates the PTSF by 100 %. Thus, it is concluded that it is necessary to either improve the TWOPAS calibration or adjust the HCM procedure to Spanish conditions. Furthermore, the TWOPAS should be calibrated and validated for the climbing lane scenario, as this was not done in the present study. According to the TWOPAS CV13 simulation results, especially in the evaluation of the climbing lane, the unusual location of the climbing lane at the end of the ramp stands out, as the PTSF and ATS results reveal greater possible benefits if the climbing lane started closer to the beginning of the ramp. The most operationally convenient location
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can be determined through a series of applications of a calibrated TWOPAS, as recommended by Valencia and García in 2010. References AASHTO, 2011. A Policy on Geometric Design of Highways and Streets, fifth edition. Washington, D. C.: AASHTO. Washington, D.C. USA. xliv + 1006 pp FHWA, 2013. Traffic Analysis Module Engineer's Manual. Federal Highway Administration. Office of Safety Research and Development, TurnerFairbank Highway Research Center, McLean, VA. September. Freedman, Z., Al-Kaisy, A. 2013. Investigation of performance and lane utilization within a passing lane on a two lane rural highway. International Journal for Traffic and Transport Engineering, 2013, 3(3): 279 – 290. Generalitat Valenciana, 2010. Puesta en servicio de la CV13 entre la CV10 (Benlloch) y la AP7 (Torreblanca). Conselleria D´Infraestructures I Transport. Valencia, España. Harwood, D. W., St. John, A. D., 1986. Operational effectiveness of passing lanes on two-lane highways. Report Nº FHWA/RD-86/196. Federal Highway Administration. April. Al-Kaisy, A, Freedman, Z. 2010. Empirical Examination of Passing Lane Operational Benefits on Rural Two Lane Highways. Journal of the Transportation Research Forum, Vol. 49, No. 3 (Fall 2010), pp. 53-68. Khan, A. M. et al., 1990. Heavy Vehicle Performance on Grade and Climbing Lane Criteria. Research and Development Branch, Ministry of Transportation. Ontario, Canada. November, pp. x + 78. Khan, A. M. et al., 1991. Cost-effectiveness of Passing Lanes: Safety, Level of Service, and Cost Factors. Research and Development Branch, Ministry of Transportation. Ontario, Canada. September, pp. xi + 124. May, A. D., 1991. Traffic Performance and Design of Passing Lanes. Transportation Research Record 1303, TRB, National Research Council, Washington, D. C., pp. 63-73. Messer C. J., 1983. Two-lane, two-way highway capacity. Final report of NCHRP Project 3-28A. Transportation Research Board. Ministerio de Fomento de España, 2016. Norma 3.1-IC. Trazado (Orden FOM/273/2016 de 19 de febrero de 2016). Internet search: http://www.fomento.gob.es/MFOM/LANG_CASTELLANO/DIRECCIONES_GENERALES/CARRETERAS/NORMATIVA_TECNICA/T RAZADO/. Morrall, J., Thomson, W., 1990. Planning and Design of Passing Lanes for the Trans-Canada Highways in Yoho National Park. Canada Journal of Civil Engineering, Vol. 17, Nº 1. Canada, February, pp. 79-86. NCHRP, 1998. Capacity and quality of service of two-lane highways. NCHRP PROJECT 3-55(3). Task 6, Enhance, calibrate, and validate the selected simulation model. TWOPAS model improvements. Transportation Research Board, 2010. Highway Capacity Manual. HCM 2010. Washington, D. C.: Transportation Research Board. USA. Valencia, V. G., Bedoya, V. E., Osorno, M. E., 1996. Relación Peso/Potencia de Vehículos Pesados en Colombia. Memorias del IX Congreso Panamericano de Ingeniería de Tránsito y Transporte. December 6. La Habana (Cuba). Valencia, V., García, A., 2010. Procedures to Facilitate Passing on Conventional Highways by Means of Simulation, Proceedings of 4th International Symposium on Highway Geometric Design. Valencia (Spain). June 1 to 5. Valencia Alaix, V. G., 2016. Elaboración de procedimientos para facilitar el adelantamiento en carreteras convencionales aplicando simulación [Doctoral tesis unpublished]. Universitat Politècnica de València. doi:10.4995/Thesis/10251/62413.
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