Estimating Texas-Mexico North American Free Trade Agreement Truck Volumes

Transcription

1 42 Transportaton Research Record 1763 Paper No Estmatng Texas-Mexco North Amercan Free Trade Agreement Truck Volumes Mguel A. Fglozz, Robert Harrson, and John P. McCray North Amercan Free Trade Agreement (NAFTA) truck traffc contnues to grow on the nternatonal trade hghway corrdors lnkng the Unted States to Mexco. Ths stuaton presents plannng challenges to accommodate NAFTA truck traffc along these hghways and at U.S.- Mexcan border ports of entry. Because transportaton data are lackng, the numbers of trucks, partcularly those carryng NAFTA trade to and from Mexco, are dffcult to estmate. Two data sources avalable for estmatng the number of trucks crossng the border are the counts of trucks crossng the brdges and the U.S. nternatonal trade data. Two methods of estmaton, each usng one of these data sets, are developed and descrbed. Two separate truck flows derved from the models are explaned and compared usng a standardzed truck type (equvalent trade truck) to represent truck flows. Interestngly, both methods provde useful outcomes. The total trade between the Unted States and Mexco contnues to grow strongly and s expected to exceed $200 bllon n Hghway ssues, both along trade corrdors and at border crossngs, contnue to attract attenton from federal and state planners. For example, the congeston along Interstate Hghway 35 north of San Antono n Central Texas s frequently attrbuted to the growth n North Amercan Free Trade Agreement (NAFTA) truck traffc along that corrdor segment. Yet the accurate measurement of truck volumes assocated wth nternatonal trade remans a challenge. Data collected at the brdges by U.S. Customs and data on U.S. nternatonal trade are not structured specfcally to answer questons about such truck volumes. The problem s complcated further because much truck border actvty s not drectly related to over-the-hghway nternatonal trade trps. McCray dd earler work on NAFTA truck trade flows and assocated hghway corrdors (1). Although estmatng trade flows from truck volumes remans challengng, an understandng must be developed of the effect of NAFTA truck volumes on trade hghway corrdors and port nfrastructure (2, 3). Ths s partcularly true gven the attenton now beng drected at both federal and state levels to dentfy and possbly fund NAFTA truck corrdors. BACKGROUND M. A. Fglozz and R. Harrson, Center for Transportaton Research, Unversty of Texas Austn, 3208 Red Rver, Sute 200, Austn, TX J. P. McCray, Unversty of Texas San Antono, 6900 North Loop 1604 West, San Antono, TX In 1998, the U.S. Department of Transportaton Southwest Regon Unversty Transportaton Centers Program sponsored an nvestgaton of U.S.-Mexcan trade corrdors, partcularly those used manly by trade trucks. The study objectve was to develop a Global Informaton System (GIS)-based U.S.-Mexco corrdor map of NAFTA truck flows based on avalable data sources usng TransCAD GIS software. The trade estmaton used a two-stage approach, whch s fully descrbed n the study report (4). As the focus of ths study, truck volumes leavng the border were frst estmated and then calbrated usng wegh-n-moton (WIM) data, whch was the focus of a prevous study (5). The ntal study used the concept of a standardzed, loaded NAFTA truck, whch s used for truck volumes n ths analyss. ALTERNATE METHODS TO ESTIMATE LOADED NAFTA TRUCKS Two methods for determnng standardzed, loaded truck volumes were evaluated. The frst method concentrated on truck numbers derved from the border brdge systems and U.S. Customs, after adjustng for varous factors. The second method used U.S. nternatonal trade data and commodty denstes, truckload weghts, and truckload volumes to determne truck flows. Ths study analyzes truck flows at a port-of-entry (POE) level; therefore the methods developed aggregate flows at brdge or border crossng levels nto POE levels, although the methods can also be appled at a brdge or crossng level when requred. Brdge Truck Volume Method Ths method s based on the brdge counts avalable from brdge authortes and U.S. Customs. At the U.S.-Mexcan border, varous economc actvtes nfluence truck volumes, ncludng those assocated wth drayage practces (.e., nternatonal tralers are drayed across the border by local truckng frms), ntermodal movements of empty and full tralers, freght consoldaton at warehouses, and actvtes that supply and consume products and servces at border ctes. Each factor has a dfferent effect on NAFTA truck volumes. Drayage practces, nvolvng tractors that often cross the border loaded and return empty, tend to grossly overstate the lkely number of trade trucks on NAFTA hghway trade corrdors. Intermodal movements from border ports to U.S. nonborder ctes, especally tralers on flat cars (TOFC), cross the brdges but do not use the trade corrdors leadng away from the border, also contrbutng to overstatng the brdge crossng counts as a measure of NAFTA truck traffc on U.S. corrdors. Freght consoldaton reduces the number of loads on the trade corrdors compared wth loads crossng the brdges. WIM data for border-crossng and hghway corrdors can be used to estmate ths consoldaton (6). Fnally, border ctes also receve some truck freght that s consumed locally and therefore does not affect NAFTA corrdors.

2 Fglozz et al. Paper No Equvalent Trade Trucks FIGURE 1 Estmaton of NAFTA trucks usng brdge truck counts. Truck Volumes on Brdges The steps n ths method are shown n Fgure 1. The assumptons underlyng ths method, as appled to ths border segment, are gven n Table 1. These data can be obtaned for southbound flows nto Mexco from U.S. brdge authortes that collect tolls and for northbound flows from U.S. Customs. Data could also be provded by WIM or truck count and classfcaton stes f a collecton process exsted at POEs. More data were avalable for northbound loaded trucks; southbound loaded trucks were reported only at the ports of Laredo and Eagle Pass. For all other ports, the percentage of southbound loaded trucks was assumed from the avalable southbound flows. Loaded Trucks Crossng Brdges The number of loaded trucks must be estmated by applyng a factor for empty trucks to the total number of trucks. Data for empty and loaded trucks crossng brdges were obtaned for ths study but may not be avalable consstently. Also, data avalablty may change as new facltes are bult and new processes are mplemented at border POEs. For example, new transportaton data are a requrement on export manfests begnnng August 1, 2000 (7). Ths study chose to standardze the varous truck types carryng nternatonal trade nto equvalent kg (80,000-lb), fve-axle, 14.6-m (48-ft) semtraler trucks (3S2), termed equvalent trade trucks (ETT). Ths truck type was selected on the bass of results from an analyss of truck types and weght statstcs that clearly ndcated the 3S2 domnated other vehcles types on NAFTA corrdors (6). Also, natonal statstcs show that for long-haul trps, semtraler trucks domnate other classes because of ther hgher effcency (8). The weght of an ETT wll depend on the commodty beng transported. In partcular, the total truck weght wll be less than kg f the commodty transported cubes out (see the Truckload Volume and Weght secton). Because both semtraler trucks and sngle-unt trucks transport trade, sngle-unt trucks must be transformed nto an equvalent number of ETT unts. The equvalence between a sngle-unt truck and an ETT must be based on weght or volume capacty per truck. Truck weght lmts are kg (32,000 lb) and kg (46,000 lb) for two- and three-axle trucks, respectvely, whereas the gross lmt s kg (80,000 lb) for 3S2 trucks, gvng a rato between 2.5 and 1.7. The rato between sngle-unt and combnaton truckloads for dfferent commodtes vares between 1.7 and 2.2, f hazardous materals commodtes are not consdered (9). A correcton must also be appled for local traffc because some truck transport s supplyng producers and consumers n each border cty and s not related to NAFTA trade. As shown n an orgn-destnaton survey at border ports, orgns or destnatons not related to nternatonal trade were less than 10 percent (10). Ths study assumes that some sngle-unt trucks carry local commerce, estmated at 33 percent n all ports except Laredo, whch s assumed to be 25 percent because t has much larger trade movements relatve to ts sze. Correcton for Intermodal Shpments In ports where ntermodal yards are present (truck-ral and truckshp), some tralers that cross the border by truck may contnue ther journey by another mode, such as TOFC. The correcton for ntermodal movements s necessary, especally n Laredo and Eagle Pass, where there are sgnfcant TOFC movements. Results An estmated total of 2,070,226 NAFTA standardzed ETT trucks crossed the Texas-Mexco border and traveled on Texas hghways durng 1997, as shown n Table 2. Ths represents an average of TABLE 1 Man Assumptons n Estmatng NAFTA Truck Volumes

3 44 Paper No Transportaton Research Record 1763 TABLE 2 Brdge Truck Volume Method Results ty volume, and truck maxmum weght. Usng the representatve densty by group (D ), truck volume (V ), and the total weght per group (W ), the number of trucks per group s calculated (N ). Commodty Group Densty The commodty group (C ) comprses dfferent commodtes j (C ). For one commodty C wth densty D, the number of loaded trucks N (wth volume V ) needed to carry the commodty weght W s 7,660 ETT trucks per day. Laredo has the largest truck volume n Texas, wth 47 and 53 percent, respectvely, for northbound and southbound movements. El Paso s next n volume, wth 22 percent of northbound trucks and 17 percent of southbound vehcles. Surprsngly, Hdalgo has the thrd-largest truck volume, wth 14 and 12 percent of north and southbound vehcles, respectvely, supplantng Brownsvlle as the leadng POE n the Texas Valley. Ths truck volume reflects the growth of maquladora operatons n the Hdalgo- Reynosa area, addng manufactured commodtes to the tradtonal agrcultural trade moved across the border. The varatons n the number of trucks at Texas border POEs relate to trade volume and the characterstcs of the dfferent commodtes beng transported. Although ths method s based on truck counts, the second method develops the numbers of trucks on the bass of U.S. nternatonal trade data. Trade Commodty Densty and Volume Method Ths method s based on calculatng truckload weght per commodty, usng commodty denstes. Representatve commodty group denstes are used, whch, when multpled by the truck capacty volume, gve the commodty group truckload. Other researchers have used a smlar approach to determne truck volumes on key hghway corrdors (11). Each truck type there has a maxmum volume and truckload weght. A crtcal densty s reached when the commodty ether weghs out or cubes out. A cubed-out commodty flls the volume of the traler but does not reach the maxmum weght. A weghed-out commodty reaches the weght lmt but does not fll the truck s volume. Consderng the total volume of the truck, a weghed-out commodty densty therefore equals the crtcal densty. Ths value s termed the maxmum practcal densty per commodty and s used n ths study to dscrmnate between the two types of loaded trucks. Method Fgure 2 s a flowchart detalng the steps of the commodty group densty method. The frst step s to separate commodtes of hgh densty, whch wll wegh out from low-densty commodtes that wll cube out. In the second step, the truck type best suted to the movement of the commodty group must be selected and the truckload volume and weght must be determned. The thrd step s to aggregate the commodtes and obtan a representatve densty for each group. It s mportant to note that when commodtes are aggregated, the representatve densty s not an average of the denstes, but a nonlnear functon of the weght proporton of each commodty, densty of each commodty, truck capac- N The total number of trucks (N ) for all the commodtes n commodty group C wll be N D The average densty (D ) per commodty group C wll be where W s the total weght of commodty group C, W D W = D V W = ( 2) D V j W = N V = W ( 4) Replacng N from Equaton 2 nto Equaton 3 results n 1 = P D j j where P s the rato of the weght of commodty j (W ) and total weght per commodty group (W ). The total number of trucks s the sum of N, whch gves the total number of loaded trucks, and a correcton factor for empty trucks and must be appled to obtan the total number of trucks on the hghway corrdor. Ths method s based on two key assumptons frst, truckloads are represented as ether weghng out or cubng out; second, a sngle commodty per truck s consdered. Varous commodtes wth dfferent denstes are n each two-dgt harmonzed classfcaton. However, for practcal reasons, t s convenent, and wthn acceptable accuracy, to categorze commodtes for ths work at the two-dgt harmonzed level, such as electroncs and chemcals, and to use ths densty to determne whether a truck would weght out or cube out. Applcaton of the Method ( 5) Trucks were estmated usng U.S. nternatonal trade data and aggregatng the data at the two-dgt harmonzed system (HS) commodty level, whch s the same commodty detal used n the Transborder Surface Freght Database (TSFD) (12). Denstes. Denstes by commodty were obtaned from an NCHRP report (13). Densty data are reported n kg/m 3 (lb/ft 3 ), wth the () 1 () 3

4 Fglozz et al. Paper No FIGURE 2 Truck weght estmaton by commodty group. same unts used hereafter. Some mportant problems appear wth the applcaton of these data: 1. Commodty denstes are gven usng the Standard Transportaton Commodty Classfcaton. Trade data are gven n Standard Internatonal Trade Code (SITC) or HS commodty classfcatons, and the match s not perfect. 2. Densty data were compled mostly durng the 1970s. For commodtes that have not had changes n producton methods or materals (e.g., agrcultural or mneral products), the value s farly accurate. However, for hghly ndustralzed products such as electrcal equpment, machnery, vehcles, and nstruments, changes n densty can be expected. As an example, the trend has been to reduce weght by replacng metal components wth lghter plastc components. These products are very mportant n U.S.-Mexcan trade, so underestmatng volumes may be expected. 3. Many electronc and electrc products were not ncluded n the NCHRP report, and ther denstes have to be obtaned from other sources (e.g., data provded by freght forwarders or brokers). Truckload Volume and Weght. Usng traler data provded by the Laredo base of Schneder Inc., truck volumes n ETTs were estmated of 48 feet long by 259 cm (102 n.) hgh and 279 cm (110 n.) wde, gvng a total of 106 m 3 (3,740 ft 3 ). Fve percent of the volume was consdered wasted, makng the usable volume 101 m 3 (3,560 ft 3 ). The total weght lmt per ETT s kg (80,000 lb), wth the weght of a tractor and an empty traler rangng between kg (32,000) and kg (36,000 lb), based on WIM data (6). The payload s therefore kg (46,000 lb), and the crtcal densty derved from kg and 101 m 3 s kg/m 3 (12.9 lb/ft 3 ). Ths s a crtcal part of the estmaton process and deserves closer attenton n future research. Even for smlar commodty groups, traler loads and denstes actually may vary between ports. Ideally, these load weghts and denstes would be dentfed by port and regon to permt a more accurate estmate of truck volumes. Usng the general method for all Texas ports probably overestmates truck volumes, whch s why calbraton usng WIM and other data s so mportant. Commodty Weght Data. Weghts at the two-dgt HS commodty level have been obtaned usng TSFD. The commodty value and weght correspond to all northbound movements, because the TSFD does not contan commodty detals at port level. Fve-dgt SITC data were obtaned by specal order from the U.S. Department of Commerce (14). Usng a concordance, these data were converted to two-dgt HS data for each port. Transborder surface transportaton data were obtaned from the Bureau of Transportaton Statstcs

5 46 Paper No Transportaton Research Record 1763 and used to prepare a table of weght-to-value relatonshps. Ths weght-to-value table was used to produce the estmated weght of each two-dgt commodty at each major U.S.-Mexcan border port. Commodty modal splt was calculated usng TSFD data. Usng these databases and estmated denstes, the number of trucks per port can be estmated at the two-dgt HS commodty level. TABLE 4 Trade Commodty Densty and Volume Method Results Results Ths study reports the densty values at the two-dgt HS commodty level used to calculate the number of ETTs. The same values are gven for loaded and empty trucks, because the average value per truck per commodty s useful n checkng the accuracy of results. These tables are too volumnous to reproduce heren, but a secton on total northbound movements s reproduced n Table 3. Ths table provdes examples for 20 two-dgt HS chapters, broken down by densty, truckload weght, trade weght, truck number, and truckload value. As expected, the truckload values vary wdely wth commodty group. Northbound, agrcultural products have an average value of $13,300, ncreasng to $85,700 for nstruments. Southbound, the range s from agrcultural products at an average value of $16,700 to nstruments at $102,900. Results by commodty group allow further calbraton of the model and more basc knowledge about trade flows and modal choce. Truckload values mght dramatcally change n comparng northbound and southbound commodtes, even n the same HS chapter. For example, HS Chapter 27 manly concerns crude ol for northbound shpments, whereas refned-ol subproducts manly comprse southbound shpments. Ths stuaton stresses the need for careful calbraton each port has peculartes n commodtes traded and drayage and maquladora effects on truck volumes that the aggregated data sometmes cannot capture. Knowledge of trade port operatons, and contacts wth carrers, brokers, customs, and freght operators, s mportant to calbrate the models at port level. Table 4 presents the results of the trade commodty densty and volume method. The second method s close n aggregate to the frst method. However, the frst method can better estmate truck volumes f more data TABLE 3 Selecton of Northbound ETTs Based on Denstes on densty and volumes, by commodty group, are collected at the varous POEs. Because trucks are loaded out to hgh levels n the second method a process not always possble n realty the current ETT method probably underestmates true truck volumes. However, because truckers strve to reach hgher levels of productvty, through ntellgent transportaton systems and other means, actual truckloads may be expected to be smlar to the truckloads used n ths analyss. Comparson of the Two Methods The results were reasonably close gven the aggregated nature of the data. The total number of estmated trucks crossng n the sx most mportant ports n Texas dffers no more than 6 percent. Nonetheless, surprsngly, vrtually the same fgures can be obtaned usng two dfferent paths wth relatvely aggregated data. Dfferences at some ports are more sgnfcant, whch suggests that further work s necessary to calbrate results at the port level. The two methods should not be seen as noncomplementary. On the contrary, each method contrbutes to a better understandng of the problem and provdes a crosscheck and bass for further analyss and comparsons at the port level. SUMMARY Fndngs were presented from an evaluaton of two methods to develop standardzed truck volumes carryng NAFTA trade to and from Mexco. The frst method, usng border-crossng volumes, s the weakest theoretcally, because numerous assumptons need to be made and the method reles on a wde varety of crucal, yet sometmes dffcult to obtan, data. Ths method forces the practtoner or researcher to gan an understandng of the complex border-crossng process and avod the temptaton to apply uncalbrated recpes or formulas. The method usng denstes and volumes shows promse and explans why results show that average value per truckload per port vares sgnfcantly. El Paso, for example, has a hgher truckload value because of the hgh proporton of electrcal products. No lnear relatonshp exsts between trade value per port and number of trucks, or between trade value and average truck weght, whch suggests that trade value alone s not enough to compare port characterstcs and ndcate trade effects on nfrastructure. Ths method would beneft from an updatng of commodty denstes and a homogenzaton of transportaton and trade commodty classfcatons. Commodty dsaggregaton provdes more nsght n the plannng analyss. Key commodty groups can be dentfed, allowng more flexblty to analyze the effects of NAFTA trade and forecast future scenaros. The methods developed can be used successfully to

6 Fglozz et al. Paper No estmate commodty truck volumes; however, a larger effort s stll requred to analyze, match, and use current trade statstcs and calbrate results. Agan, the accuracy and detal of avalable data greatly affect the qualty of results. Fnally, further analyses of traler loads n relaton to commodty denstes and volumes that are crossng border ports wll enable more accurate standardzed ETT volumes to be determned. Such data are mportant because they can be ncorporated nto federal and state plannng actons that address the mantenance, rehabltaton, and reconstructon of desgnated nternatonal trade corrdors n the Unted States. REFERENCES 1. McCray, J. P. The Rvers of Trade: U.S.-Mexco Trade Truck Transportaton Corrdors. Proc., 37th Annual Meetng of the Transportaton Research Forum, Chcago, Ill., McCray, J. P. North Amercan Free Trade Agreement Truck Hghway Corrdors: U.S-Mexcan Truck Rvers of Trade. In Transportaton Research Record 1613, TRB, Natonal Research Councl, Washngton D.C., 1998, pp Harrson, R., L. Boske, and J. P. McCray, Transportaton Issues and the U.S.-Mexco Free Trade Agreement. Research Report F. Center for Transportaton Research, Unversty of Texas Austn, Feb Fglozz, M. Truck Trade Corrdors Between the U.S. and Mexco. Southwest Regon Unversty Transportaton Centers Research Report /1. Center for Transportaton Research, Unversty of Texas Austn (n press). 5. Fglozz, M. A., R. Harrson, and J. P. McCray. Usng Wegh-n-Moton Data to Calculate NAFTA Truck Volumes n Texas. Presented at the 79th Annual Meetng of the Transportaton Research Board, Washngton, D.C., Harrson, R., L. A. Sanchez-Ruz, and C. E. Lee. Truck Traffc Crossng the Texas-Mexco Border. In Transportaton Research Record 1643, TRB, Natonal Research Councl, Washngton D.C., 1998, pp Bderman, D. New Rules for Exports. Journal of Commerce Week, Vol. 1, No. 8, 2000, pp Natonwde Truck Actvty and Commodty Survey, FHWA, U.S. Department of Transportaton, June Commodty Movements on the Texas Hghway System: Data Collecton and Survey Results. Texas Transportaton Insttute, Texas A&M Unversty, College Staton, Tex., Nov Transportaton Aspects of the Maquladora Industry Located on the Texas-Mexco Border. Research Report F. Texas Transportaton Insttute, Texas A&M Unversty, College Staton, Tex., Bole, M. P., S. Benson, and J. Rownsk. Freght Flow Forecastng An Applcaton to New Jersey Hghways. Journal of the Transportaton Research Forum, Vol. 39, No. 2, Sprng Bureau of Transportaton Statstcs. Aprl 2, NCHRP Report 260: Applcaton of Statewde Freght Demand Forecastng Technques. TRB, Natonal Research Councl, Washngton D.C., U.S. Exports to and Imports from Mexco. Foregn Trade Dvson, U.S. Department of Commerce, Publcaton of ths paper sponsored by Commttee on Internatonal Trade and Transportaton.