Big Ten Curve Railroad in Arvada — Online Webcam Traffic

What is Big Ten Curve and where is it located

In the foothills of Colorado, on the border between the plains and the Rocky Mountains, lies one of the most unusual railroad structures in the American West — Big Ten Curve. It is an S-shaped 270-degree curve consisting of two loops — Big Ten Loop and Little Ten Loop — where each curve has a 10-degree deviation per 100 feet of track. The camera is located in the city of Arvada, approximately 19.5 miles west of Denver's Union Station, in an area that is now part of the Denver metropolitan area.

The facility is located on Union Pacific's Moffat Tunnel Subdivision — a single-track mainline with CTC and ABS systems that serves as the only direct rail route from Denver westward through the Continental Divide. It is here that the Great Plains begin their ascent toward the Front Range, and the railroad must wind its way to gain elevation.

Construction history: how the famous curve came to be

In the early 1900s, Denver found itself in transportation isolation. The main transcontinental lines of Union Pacific ran through Cheyenne to the north, and the city needed its own route to the Pacific Coast. In 1902, the Denver, Northwestern and Pacific Railway began laying track through the foothills. Engineer Sumner faced a challenge: how to raise trains 600 feet in elevation over less than 3 miles without exceeding the allowable grade.

The solution proved elegant — instead of a direct 4% grade climb, the route was stretched to approximately 3 miles (about 16,500 feet of track) through a series of 10-degree curves. This reduced the average grade to 1.8%. The company changed hands several times: in 1926 it became the Denver & Salt Lake Railroad, in 1931 it passed to the Denver & Rio Grande Western Railroad, and today it belongs to Union Pacific. Each of these operators contributed to the development of the infrastructure.

Engineering features of the curve

The design of Big Ten Curve is unique even by the standards of U.S. mountain railroads. The series of 10-degree curves creates a characteristic S-shaped profile that is clearly visible from the air and on satellite imagery. Trains pass through this section at limited speed, with locomotives working hard to overcome the grade.

The main problem at this location is strong mountain winds that can literally blow trains off the tracks. Until 1971, incidents occurred regularly here. Then D&RGW installed a unique wind barrier — old grain hopper cars filled with earth were lined up along the inside of the curve. This solution proved effective and still protects trains from wind gusts that reach considerable force in the foothills.

Transportation significance of the route

Big Ten Curve is not just a scenic curve — it is part of a critical transportation artery. The Moffat Tunnel Subdivision is the bottleneck for westward traffic from Denver. The single-track section handles heavy freight routes where trains gain over 4,000 feet of elevation over approximately 50 miles at a grade of no more than 2%.

This route bypasses the traditional path through Tennessee Pass and provides a more efficient connection between Denver and the Pacific Coast. Today, coal and grain freight trains pass through here, as well as the famous Amtrak California Zephyr passenger train, running between Chicago and San Francisco.

Trains that pass through the curve

The section's capacity is about 6 trains per day. These can be heavy Union Pacific coal trains from Wyoming mines, grain hoppers, BNSF container trains using the route through trackage rights, and of course the passenger California Zephyr — one of America's most scenic trains.

For rail enthusiasts (railfans), Big Ten Curve is a legendary spot. Here you can watch long trains slowly wind through the loop while locomotives work at full power on the grade. The PTZ camera function allows you to track a train throughout the entire curve.

Infrastructure around Arvada

The area where the camera is installed lies at the foot of the Front Range foothills, where the Great Plains transition into mountains. The nearest railroad infrastructure includes Clay Siding, Tunnel 1, and the famous 6.2-mile Moffat Tunnel, through which trains pass beneath the Continental Divide.

Parallel to the railroad runs the I-70/US 6 transportation corridor, connecting Denver with mountain resorts. Arvada itself is a Denver suburb with a population of about 120,000, preserving its historic center and actively developing in recent decades. The Central Corridor railroad connects Denver with the West Coast and is a strategic freight artery of national importance.

What you can see on the camera

The camera is positioned so that the frame captures a curved section of railroad track stretching across the horizon through open grassy terrain. In the background, the Front Range foothills are visible; in the foreground, there is a fence along the tracks and the distinctive wind barrier made of earth-filled rail cars. When a train passes — which happens several times a day — you can watch the consist slowly move along the curve, the locomotive on the grade leaving a trail of smoke (if it's a freight train), and the cars winding like a snake. The PTZ camera function allows you to zoom in on areas of interest and examine details — from the locomotive type to the cargo on open flatcars.