According to the manual, where do most bus accidents happen?

49 CFR 383.117(a)(6), operating practices and procedures not otherwise specified; AAMVA CDL Manual Section 4.3.3 (p.4-3)

Knowing that intersections are the single most common bus-accident location reinforces why extra caution there, beyond just obeying signals, is part of the passenger-endorsement knowledge expected on the test.