Your straight truck is carrying 5 pounds of Division 2.3 chlorine, well under the quantity that would require placarding, and no placards are displayed. Approaching a railroad crossing with crossbucks but no gates, are you required to make the full stop under 49 CFR 392.10?

49 CFR 392.10(a)(2)

Chlorine gas is severely toxic even in small releases, so the rule drops the usual placarding-quantity threshold entirely for this one material. A driver who reasons 'it's under the placard limit, so the special rules don't apply' is applying the wrong test — for chlorine, any quantity at all triggers the mandatory railroad-crossing stop.