They were initially classified as AM3 units before the introduction of the TOPS classification system , and were the dominant ORGANIZATION@1 on the LOCATION@1 suburban railway network for over NUMBER@1 years before being progressively phased out by newer rolling stock .

At first they were classified as AM3 units before the introduction of the TOPS classification system . They were the dominant ORGANIZATION@1 on the LOCATION@1 suburban railway network for over NUMBER@1 years .
