Trends in Northbound Freight Traffic at Arizona’s Border Ports of Entry

The volume of truck containers outstrips trains, but train containers are rising rapidly

When assessing trade between the US and Mexico, or more specifically, between Arizona and Mexico, the focus has been most frequently on dollar amounts and kinds of merchandise imported or exported. Such trade data are commonly used as indicators of a region’s competitive advantage and the overall strength of economic interconnectedness between two regions. However, data showing only trade figures tend to conceal the dynamics of a complex movement of merchandise across the border. To shed some light on the ways and means by which merchandise is brought from Mexico into the US through Arizona’s ports of entry (POEs), this article will analyze border crossings of truck and rail cars. Data are obtained from the Bureau of Transportation Statistics (BTS), and as indicated in the title, are available only for northbound border crossings.[1]

Trucks deliver most of the freight across the border

About 80 % of all land-bound freight across the US-Mexico border is being delivered by trucks, the rest by rail cars. In Arizona, the share of truck-borne freight was over 90% in the late 1990s, but since 2000 has varied between as low as 82.0% (in 2013) and as high as 88.7% (in 2017) of the total volume of northbound container crossings.[2] Trucks deliver merchandise across five of Arizona’s six ports, while the rail-borne freight crosses the border only at Nogales.[3] The Nogales railroad crossing was opened in 1882 as the first along the entire US-Mexico international land boundary, but today accounts for less than 7% of the US-Mexico train crossings. Today, nearly 75% of all trains from Mexico pass through the Texas ports of Laredo and Eagle Pass. [4]  

Figure 1 compares annual volumes of border crossings through Arizona’s POE during the last twenty-six years. It clearly shows the dominance of trucks in delivering freight across the border, as well as an increasing gap between the two modes of transportation. In 2022, a total of 80,447 crossings were made by rail cars from Mexico into Arizona, compared to 457,106 crossings of containers delivered by trucks.

Figure 1. Northbound Crossings of Truck and Rail Containers from Mexico into Arizona, 1996-2022

Volume of rail containers increased relatively more than truck containers

While the volume of rail containers carrying freight over the border remains overshadowed by the volume of truck containers, it is interesting to note that the rail crossings recorded higher overall growth than the truck crossings, as illustrated in Figure 2. The volume of rail containers crossing the Arizona border increased from 25,352 in 1996 to 80,447 in 2022 (an increase of 217.3%) compared to a 63.1% increase in truck-container crossings from 280,187 to 457,106 in the same period. Particularly noticeable is an increase in the second decade of the 21^st century, which corresponds to the expansion of the automotive industry in Sonora. A portion of assembled cars from Ford’s Hermosillo Stamping and Assembly Plant has been shipped by train north to the US market via Arizona.[5]

Figure 2. Northbound Crossings of Truck and Rail Containers from Mexico into Arizona, 1996 = 100

Border crossing dynamics differ between truck and rail transportation mode

Because trucks carry different freight from the kinds of merchandise shipped by rail, it is no surprise to find that the annual variations in the crossings differ between the two modes of transportation. As shown in Figure 3, rail crossings show greater variations from year to year than truck crossings.  The peaks and lows in rail crossings from year to year are higher or deeper than the changes in truck crossings. The fact that fresh produce from Mexico is shipped almost exclusively by trucks contributes to a relatively flatter pattern in annual data for truck crossings. This was especially evident during the COVID pandemic when manufacturing shipments were more affected than fresh produce. In 2020, truck crossings declined 1.3% from 2019 compared to a 16.6% drop in rail crossings. But, as trade in transportation equipment rebounded in 2021, rail crossings increased by 16.1% compared to 9.2% in truck crossings.

Figure 3. Northbound Crossings of Truck and Rail Containers from Mexico into Arizona, Annual Change (%)

Empty containers’ share of border crossings

Up to 30% of all containers carried by trucks in the northbound direction are empty. As shown in Figure 4, since 1996, i.e. the early years under NAFTA, through 2020, the number of empty truck crossings through Arizona POEs has stayed rather constant between 88,000 and 93,000 crossings annually. Since 2020, the number of empty truck crossings increased for the first time to over 121,000 crossings, and with 135,547 crossings in 2021, accounted for 29.5%, the largest in the last two decades. The last time empty truck containers accounted for more than 30% was in the late 1990s.

In comparison with trucks, empty rail containers account for a higher share of northbound rail crossings ranging between 30% and 40% on an annual basis. Since 2013, their share had increased and from 2018 through 2020, empty rail containers surpassed the volume of loaded containers.  

Figure 4. Northbound Crossings of Truck and Rail Containers from Mexico into Arizona, by Load

Different volumes of loaded vs. empty containers in truck and rail crossings foremost reflect differences in the kinds of products shipped by each mode. For example, most of the rail cars that carry copper ore and concentrates across the border from Arizona to Mexico return empty since they are structurally unsuitable for transporting cars that are shipped by rail in the opposite direction.[6]

In the case of truck crossings, the existing US restrictions on Mexican carriers present another important factor impacting the overall volume of crossings, as well as the ratio of loaded vs. empty trucks.  Although the number of Mexican carriers that are allowed to operate long-haul routes across the border has increased,[7] a significant volume of truck freight is still being forwarded across the border by the drayage system.  This practice, by which drayage trucking companies located near the border drive freight back and forth between trans-loading facilities all day, has been in place since the inauguration of NAFTA and basically has remained unchanged under its replacement, USMCA.  Surveys of drayage drivers have indicated that most drivers preferred making frequent repeated trips across the border rather than wasting time on the other side of the border while waiting for opportunities of picking up return freight.[8]

Nogales Port: Monthly variations in truck and rail crossings

Figure 5 shows monthly crossings of rail containers from January 1996 through December 2022. Aside from a generally upward, although somewhat slow-moving trend line, the pattern has remained rather steady characterized by a substantial volume of empty container crossings. Although volumes of crossings differ from month to month, the differences between low and high points do not seem to be very large.

Figure 5. Monthly Crossings of Rail Containers, Northbound at Nogales Port, 1996-2022

In contrast, truck crossings at the Nogales port display a substantial variation in volumes between winter and summer months, as shown in Figure 6. This has been a well-known unique characteristic of the Nogales port due to the seasonality of fresh produce shipments from Mexico. During the winter months, which are the fresh produce high season, the average number of loaded truck crossings is more than 10,000 above the average monthly number of crossings during the summer months. The proportion of loaded containers vs. empty ones also increases substantially during the winter season. This in turn suggests that empty container crossings are primarily associated with the cross-border flow of manufacturing and other non-agricultural freight.

Figure 6. Monthly Crossings of Truck Containers, Northbound at Nogales Port, 1996-2022

The “fresh produce effect” on loaded truck crossings

While data on trucks specifically carrying fresh produce are not available, a rough estimate of their volumes is calculated as a difference between an average number of crossings in winter months and average number of crossings in summer months.[9] As shown in Figure 7, volumes of loaded truck crossings in the winter months are substantially higher (at times almost double) than average volumes during summer months. This difference stems primarily from the increased crossings of trucks loaded with fresh produce during the winter season.

Figure 7. Loaded Truck Crossings at Nogales: The “Fresh Produce Effect”

Post-COVID trends: Back to “normal” and more

Loaded truck crossings resumed their typical pattern in the second half of 2022 after some ups and downs at the beginning of the post-COVID year, as shown in Figure 8. Since July, in every month through the end of the year, the volume of loaded truck crossings exceeded the pre-COVID year 2019 level, although by a small number.[10]

Figure 8. Monthly Crossings of Loaded Truck Containers at Nogales Port of Entry

As shown in Figure 9, the post-COVID crossings of loaded rail cars exceeded the 2019 volumes in every month of 2022. They also restored the monthly dynamics of the pre-COVID flow.

Figure 9. Monthly Crossings of Loaded Train Containers at Nogales Ports of Entry

Nogales keeps the 5^th and 6^th place among US-Mexico ports of entry

In comparison with other major POEs along the US-Mexico border, Nogales has retained its pre-pandemic 5th place in the total volume of rail crossings in 2022, as shown in Table 1. All other POEs also kept their rankings, although some failed to recover the 2019 volumes. In fact, only Nogales, Laredo, and Calexico East experienced increases in rail crossings above those in 2019. The above-average increase also resulted in an increase of Nogales’ share from 6.3% to 7.2% of the total rail crossings in 2022.

Table 1.  Northbound Rail Crossings via US-Mexico Ports of Entry (Empty & Loaded Containers)

With close to 375,000 truck crossings in 2022, Nogales has kept its pre-pandemic 6^th place among the major US-Mexico POEs, as shown in Table 2.  With only 4.1% increase over 2019, Nogales’ post-COVID recovery trailed behind the ports of Santa Teresa, Calexico East, Eagle Pass, Laredo, and Otay Mesa, but fared better than Hidalgo, Brownsville, and El Paso.   

Table 2.  Northbound Truck Crossings via US-Mexico Ports of Entry (Empty & Loaded Containers)

Note that Table 2 reveals a new addition among the ten major border crossings for trucks coming northbound from Mexico: the port of Ysleta.  Located at the Ysleta-Zaragoza international bridge on the east side of El Paso, it was designed as a separate and distinct port by the Customs and Border Protection (CBP) in 2020. Like the Santa Teresa port (in New Mexico, but not far from El Paso) several years ago, the Ysleta port was opened for the purpose of relieving the congestion at the El Paso port.[11] The records of increased crossings at both the Santa Teresa port and at the Ysleta port largely explain the “mystery” of drastic declines in trade and commercial crossings at El Paso port noticeable in recent data.