By Christina Sessions
Alaska Journal of Commerce

The Alaska Railroad Corporation recently completed the first phase of a noise and vibration study for the corridor that runs between the airport spur and the rail yard in downtown Anchorage.

The study will help the railroad determine the best course of action to help relieve the congestion on one of its busiest corridors.

According to a press release from the railroad, the section of rail between the airport and downtown has seen a significant increase in passenger traffic and the railroad is projecting more growth in the future.

The purpose of the study was to provide the railroad with information regarding how capital improvement projects will likely affect area neighborhoods. Some of the improvements under consideration include installing automated signals and switches, additional passing lanes, and double tracking that section of the rail. The railroad is currently double tracking the section between Minnesota Drive and 120th Street in South Anchorage.

Once the corporation evaluates each improvement possibility, it will seek public comment. This will likely happen in the fall, according to Pat Flynn, spokesman for the railroad. The corporation is in the process of presenting the findings of the study to area community councils.

During the study ambient noise measurements were taken at eight sites along the corridor over three one-week periods in March, May and June. Noise and vibrations measurements were taken on a total of 86 trains.

One key finding of the study was that the noise level was higher in the spring and summer than in the winter. The railroad attributed this to a number of factors including increased number of trains in the summer, increased outdoor activity, increased aircraft noise and lack of snow cover.

Vibration measurements were taken in three different types of soil -- clay, peat and sand. The study concluded that ground-borne vibrations traveled better in clay and peat but did not travel as well through sand. Another conclusion was that in the winter when the ground was frozen the vibrations travel similar to the vibrations through sand in the summer -- in all types of soil.

Speed was another factor in the vibration study. Loaded gravel trains traveling at higher speeds would increase the level of vibration. This means that the corporation will strictly enforce the 15-mph speed limit through the corridor for loaded gravel cars, according to the press release.

The speed of passenger cars, on the other hand, had little effect on vibration, so the railroad will consider increasing the speed of passenger trains through the corridor to help alleviate congestion. Homes beyond 150 feet of the track in sandy soil or 300 feet in peat and clay were not likely to feel ground-borne vibrations, the study found.