After your PPE is on, the priority is to secure the work zone and control traffic. Positioning a vehicle upstream creates a protective barrier between the crew and oncoming traffic and establishes a buffer area where you can work safely. The vehicle also serves as a visual warning to approaching drivers, helping to slow and steer them away from the site. Cones are useful for outlining the exact work area, but they’re most effective once the vehicle barrier is in place. Breaks or rechecking weather don’t address the immediate safety needs of the scene. So the next setup action is to place a vehicle upstream to shield the crew and set up safe working conditions.

Current is the rate at which electric charges flow through a conductor, so its unit is the ampere. One ampere means one coulomb of charge passing a point each second. That direct relationship—coulombs per second—defines the current unit, written as amperes (A). Volts measure electric potential difference (the pressure that pushes charges), ohms measure resistance (how much a material resists the flow), and watts measure power (the rate energy is used or transferred). Since the question asks about the unit for current, amperes is the correct choice.

Starting with advance warning signs and then moving down toward the work site creates a clear, proactive path for drivers. This setup gives motorists plenty of notice before they reach the work zone, allowing them to slow down, change lanes if needed, and follow the designated path through the area. It establishes a predictable flow from far upstream to the work zone, so drivers aren’t surprised by abrupt changes and can adjust gradually as they approach the site. The sequence also supports effective tapering of lanes and proper channelization, which keeps workers safer by reducing sudden lane shifts and rear-end collisions. If you skip the early warning step or start near the work site, drivers won’t have time to react, and the traffic flow can become chaotic. Placing all devices without regard to order would remove the essential progression that guides motorists safely from the approach to the end of the zone. Merely posting stop signs at the ends doesn’t provide the continuous guidance and speed management needed to navigate through the entire work area safely.

A de-energized system can become energized through several real-world paths, not just by someone flipping a switch. Energy can re-enter via backfeed from measurement and protection devices, like potential transformers that energize a circuit they’re monitoring when there’s a source elsewhere feeding the system. Unknown or undocumented power sources, such as unreported generators or customer equipment, can also energize a circuit if they’re connected to it. If lockout and tagging were missed, equipment can be re-energized while someone is working, because there’s no approved isolation preventing it. Test equipment itself can fail or introduce unintended connections, momentarily energizing parts of the system. A lightning strike can drive surge energy into lines, creating energized paths where none were expected. When an energized line contacts a de-energized line, current can flow into the latter and energize it. Insulation failure can create a conductive path that allows voltage to appear on conductors or equipment that were supposed to be de-energized. Because each of these are plausible energizing paths, the best answer is that all of the above cover the ways a de-energized system can become energized. In practice, this is why thorough switching procedures, proper lockout/tagout, and verification of absence of voltage with tested equipment are essential before any work.