Fe Railroad to cease operation of the Grand Canyon Railway in 1968 (only three passengers were on the last run). The railway was restored and service reintroduced in 1989, and it has since carried hundreds of passengers a day. Trains remained the preferred way to travel to the canyon until they were surpassed by the auto in the 1930s. By the early 1990s more than a million automobiles per year visited the park. West Rim Drive was completed in 1912. In the late 1920s the first rim-to-rim access was established by the North Kaibab suspension bridge over the Colorado River. Paved roads did not reach the less popular and more remote North Rim until 1926, and that area, being higher in elevation, is closed due to winter weather from November to April. Construction of a road along part of the South Rim was completed in 1935. Air pollution The primary mobile source of Grand Canyon haze, the automobile, is currently regulated under a series of federal, state and local initiatives. The Grand Canyon Visibility Transport Commission cites U.S. government laws regulating automobile emissions and gasoline standards, often slow to change because of the automobile industry's planning schedule, as a primary contributor to air quality issues in the area. They advocate policies leaning toward stricter emission standards via cleaner burning fuel and improved automobile emissions technology. Air pollution from those vehicles and wind-blown pollution from Las Vegas, Nevada area has reduced visibility in the Grand Canyon and vicinity. During the past decade, various regional coal-fired electric utilities having little or no pollution control equipment were targeted as the primary stationary sources of Grand Canyon air pollution. In the 1980s the Navajo Generating Station at Page, Arizona, (15 miles away) was identified as the primary source for anywhere from fifty percent to ninety percent of the Grand Canyon's air quality problems. In 1999, the Mohave Generating Station in Laughlin, Nevada, (75) miles away settled a long-standing lawsuit and agreed to install end-of-point sulfur scrubbers on its smoke stacks. Closer to home, there is little disagreement that the most visible of the park's visibility problems stems from the park's popularity. On any given summer day the park is filled to capacity, or over-capacity. Basically the problem boils down to too many private automobiles vying for too few parking spaces. Emissions from all those automobiles and tour buses contributes greatly to air pollution problems.