Worked Example: Signposting a Local Detour Drivers Actually Follow

Detour signage that drivers actually follow tells a stranger which way to go at every decision point on the route, from the first warning to the END DETOUR sign. Plan it from the TGS, give drivers advance notice, drive it as someone with no local knowledge before opening, and patrol it all through the closure.

This is an example scenario, walked through from planning to reopening. It is not a real job, council or incident. It is written for supervisors, implementers and project engineers responsible for local road closures. It is not engineering advice: the traffic guidance scheme (TGS) and detour plan must be prepared by a suitably qualified person and approved by the road authority. For the planning side of closures, see our guide to road closure and detour plans.

The example closure

Example scenario: a water utility contractor needs to replace a pipe crossing that runs under a local road. The road must be fully closed for three days.

• Closed road: a two-lane local connector, posted 50 km/h, used as a short cut between two collector roads.
• Closure point: mid-block, with houses on both sides and a small group of shops at one end.
• Detour: about 1.5 kilometres, via a collector road, a roundabout and a second local street, rejoining the closed road at its far end.
• Traffic: local cars, a few delivery trucks, one bus route that already runs on the collector, and some through traffic using the road as a short cut.
• Constraints on the detour: one street on the obvious alternative route has a load limit, and another is a cul-de-sac that looks like a through road from the closure.
• Crew: a supervisor with the implementation ticket, TC 1 at the closure for resident access, and a second crew member to set up and patrol the detour.

The TGS and detour plan are approved by the council. The designer has checked the detour for heavy vehicles and excluded the load-limited street.

Two weeks out: advance notice

Most drivers who ignore a detour did not know it was coming. In the example, the contractor arranges:

• Resident and business letters a week before, with the dates, the detour map and a contact number. See our resident notification template.
• VMS boards on both collector roads about a week before, showing the closure dates, then switched to the detour message on the day. Our guide to VMS boards covers message rules and placement.
• Council notice to the bus operator and waste services, and to emergency services as the approval requires.
• Online notice through the council's roadworks page, where it has one.

The decision point audit

The core of good detour signage is simple: list every point on the detour where a driver has to choose, and make sure there is a sign that answers the question. The supervisor does this with the detour plan and a drive of the route the week before.

Points D and E are the lessons in this example. Point D is the classic: drivers see a DETOUR arrow on the approach to a roundabout, then have no sign at the exit they need. Point E is a local trap: the cul-de-sac is the wider, straighter road. Without a clear arrow and a NO THROUGH ROAD sign, drivers follow the road that looks right and end up turning in someone's driveway. The designer approved the extra signs before the closure, and the change was recorded. Our guide to changing a TGS on site explains how to handle that properly.

Day one: set-up order

The closure goes in at 7 am. Set-up order matters because the detour must be in place before the road closes, or drivers are sent into a closure with no way around it.

1. Detour signs first, starting from the far end (END DETOUR) and working back to the start, so that once the start signs go up the whole route is already signed.
2. Advance warning signs on both collector roads.
3. Permanent signs that contradict the detour covered, as the TGS shows, such as a direction sign pointing to the closed road. See covering permanent signs at roadworks.
4. VMS boards switched to the detour message.
5. Closure barriers and ROAD CLOSED signs at both ends of the closed section, with the local access arrangement.
6. Work area set up inside the closure.

Then the stranger's drive. The supervisor asks a crew member who has never driven the area to follow the detour with no map and no phone navigation, from each direction, while the supervisor rides along and says nothing. Any hesitation is a missing or unclear sign.

During the closure: what goes wrong and the fix

Day one, 8:15 am. Satellite navigation. Delivery vans keep arriving at the closure, sent there by navigation apps. TC 1 directs them to the detour. The supervisor adds a short note to the VMS message and asks the council whether the closure is listed on the traffic information services it uses. Controllers keep directing in the meantime.

Day one, 11:30 am. A truck at the cul-de-sac. A small rigid truck takes the cul-de-sac fork despite the signs, because the driver read only the street name. It cannot turn and has to reverse out, with the crew member on patrol helping as a spotter. The supervisor checks the sign is visible from a truck cab and adds a second NO THROUGH ROAD sign closer to the fork.

Day one, 3:30 pm. A rat-run. Residents in a nearby narrow street complain that through traffic is using their street as a short cut instead of the signed detour. The supervisor drives it, confirms it, and calls the designer. The approved response is a sign at the rat-run entry pointing back to the detour. Signs cannot close a public street that is not in the approval, so the response is guidance, not a barrier.

Day two, 6:45 am. A turned sign. On the morning patrol, the DETOUR sign at the roundabout exit has been turned to face the wrong way, overnight, by wind or by hand. Drivers would have been sent the wrong way at dawn. It is turned back, ballasted better and checked again at mid-morning. This is why patrols matter.

Day two, 10:00 am. Residents' access. A resident inside the closure needs to leave for a medical appointment. TC 1 has a briefed process: check the work area is safe, walk the vehicle out through the controlled access point, record the time. Emergency services have access at all times.

The patrol and record template

Detour signs are inspected as part of the traffic control: at the start and end of every shift, at suitable intervals during it, and overnight checks where the TGS or approval requires them for a closure that stays in place.

Add a photo of each sign from the driver's position at each patrol, so the record shows what the driver saw.

Common detour signage mistakes

These are the faults a seasoned supervisor looks for on every detour, whether or not they turned up in this example.

Reopening and removal

On day three the work is finished and the road reinstated. Reopening runs in the reverse of set-up: work area cleared, closure barriers removed, the closed road driven through both ways, then the detour signs removed from the start of the detour towards the END DETOUR sign, so drivers already on the detour are not left without guidance. Covers come off the permanent signs, the VMS boards switch to a message that the road is open or are switched off as planned, and the final patrol confirms nothing is left behind.

For guidance on signs and detours, check Austroads, Transport for NSW in NSW and VicRoads in Victoria.

Next steps

Before your next closure, list every decision point on the detour, drive it as a stranger before opening, and patrol it every shift. To estimate how much extra travel the detour adds, try the free detour calculator.