The cracks in the CTA elevated structure developed on a curve where the rapid transit tracks pass over the Rock Island Railroad's commuter right-of-way near 18th and Clark Streets. Because of the danger of the structure collapsing, the Rock Island suspended service to La Salle Street Station. The first of the cracks was spotted Wednesday morning by Vernon Solarie, a bridge engineer for the Rock Island, as he rode to work in the upper deck of a Rock Island commuter train that passed under the elevated structure. Solarie, 46, a native of Columbia, has worked for the Rock Island for 21 years and will be awarded the Chicago Metal of Merit and a certificate of recognition from the Rock Island. Mayor Bilandic said the Metal of Merit will honor Solarie for vigilance and interest in the health and safety of his fellow citizens. The Chicago Transit Authority plans to conduct a test run over the cracked section of the Dan Ryan line elevated sturcture Sunday to determine if it can be opened Monday morning. Marshall Suloway, Chicago Commissioner of Public Works, said that the test train will not run until the structure (built in 1968), dangerously weakened by a series of large cracks in steel girders, is considered to be safely shored up by emergency repairs.