High-mast lighting on I-635High lights. Ground-level repairs.

The roadway photograph is full of light: bright pavement, illuminated slopes and lamps reaching well above the road. In February 1970, Texas Highways presented these tall poles as an advance in highway illumination. For a driver approaching a complicated interchange after dark, the useful question was what the lighting made visible ahead.

The article describes two installations at opposite ends of an 8.9-mile section of I-635 across north Dallas. Five 150-foot poles served the three-level I-35E interchange at the west end. Eight served the two-level interchange with US 75 at the east end. Between them, 164 shorter, 50-foot poles carried conventional lights in the median. The corridor combined two lighting methods rather than using the tallest poles everywhere. The two installations

The Texas Transportation Institute’s February 1969 research report helps explain the approach. Its authors wanted drivers to see roadway geometry, surrounding terrain and obstacles far enough ahead to plan a maneuver. They treated uniform light and control of glare as design requirements. Brighter pavement alone was not the whole objective. The night photograph illustrates the broad coverage the magazine promoted. Lighting objectives, pp. 3–7

A person standing beside the concrete base gives the scale away. These were heavy structures: the magazine reports 12,000 pounds of steel in each pole. Four galvanized sections were fitted together with hydraulic jacks, with no welding at the job site. The octagonal shaft narrowed from 27.5 inches at its base to six inches at the top. Pole construction

The magazine credits Highway Department engineers with the design and E. M. Carl with its basic concept. It also describes prototype testing at the Texas Transportation Institute. The institute’s earlier report independently lists two completed Dallas installations using 150-foot poles and hoisting devices among projects in several states. This was an emerging highway practice with research and field installations behind it. Contemporary installation list, pp. x–xi

Carl thought the Dallas poles might be the world’s highest. The magazine quotes his belief, then discusses taller poles planned for Houston. Height made an easy headline. The more demanding problem was placing and aiming the lamps so that their light overlapped usefully across the ground.

The photograph of the lowered ring is the most revealing detail. Ten 1,000-watt floodlights sat on a circular steel assembly, but they did not have to stay 150 feet up for servicing. An internally mounted electro-hydraulic winch lowered the ring to ground level. The close view shows the lamps clustered around the shaft within reach of workers. The lowering system

That mechanism remains part of the maintenance story. TxDOT’s later Highway Illumination Manual calls for inspecting the entire pole and lighting assembly whenever the ring is lowered for maintenance. Its instructions also require replacement fixtures to match the specified equipment and preserve their aiming. They show why a lowering ring and properly directed lamps continue to matter. Later inspection guidance

The 2001 aerial view of I-635 at I-35E puts the west installation’s location in a wider setting. The ramps occupy an extensive piece of ground. Lighting that space was one task; keeping the lighting serviceable was another. The ring photograph brings the latter down to a scale a worker could handle.