In the Japanese Lane Load Specification, the distributed live load intensity on secondary lanes should be what percentage of the live load on main lanes?

• A. 25%
• B. 50%
• C. 75%
• D. 100%

Answer: (B)

Secondary lanes carry traffic that, on average, imposes less live load than the main lanes, so the load they contribute is taken as half of the main-lane live load. This choice in the Japanese Lane Load Specification reflects how wheel loads are shared across multiple lanes and helps keep designs safe yet economical for girders that support several lanes. If the secondary-lane load were assumed much smaller, the design could be unsafe because the structure wouldn’t be adequately prepared for the combined effects of loading across lanes. If the secondary-lane load were treated as equal to the main-lane load, the design would become unnecessarily conservative and more costly. Therefore, the standard is to use half of the main-lane live load on secondary lanes.