Are your lane closures or Temporary Traffic Management (TTM) setups still getting breached by vehicles driving through them at speed?

That’s the challenge the team at Auckland System Management  (ASM) faced during a recent maintenance project at the Johnstone Hill Tunnels on SH1. Despite a well-planned TMP, vehicles were still speeding, veering into cones, and ignoring lane changes, putting crew and other road users at risk of harm.

What if a simple, portable tool could eliminate that risk overnight?

So they tried something new: a live trial of portable rumble strips supplied by Vanguard. When vehicles drive over the rumble strips, they make drivers aware that something is about to change.

In this case study, Fiti Potusa, TTM Operations Manager for ASM, shares what worked, what didn’t, and why they’re now looking to make portable rumble strips standard equipment.

The Problem: Drivers Breaching a High-Risk Tunnel Closure

Six months before the trial, ASM (a joint venture between Fulton Hogan, HEB Construction and NZTA Waka Kotahi) was managing a complex contraflow at the twin Johnstone Hill Tunnels, north of Auckland. Vehicles needed to switch sides of the road through crossovers while one tunnel was closed for maintenance. But the setup wasn’t working:

“We had around six closure breaches… people were not following the cone line or the signs,” said Fiti Potusa, TTM Operations Manager.

Drivers missed the crossover, hit cones, or lost control completely. Even with barriers, Truck Mounted Attenuators (TMA), signage, and strict adherence to the Traffic Management Plan (TMP), inattention and speed were creating serious safety risks.

Image: A car missing the crossover point (before the rumble strip trial) and hitting the side barrier on the opposite lane.

What Are Portable Rumble Strips?

Portable rumble strips are temporary, self-weighted rubber strips designed to be placed on the road surface to deliver a tactile and audible vibration when vehicles drive over them.

Their purpose? Increase driver attention to the road, especially in areas with changing alignment, reduced speeds, or unexpected closures like:

• Contraflows
• Stop/Go operations
• Tunnel or night works..

Unlike permanent rumble strips milled into the asphalt, portable rumble strips weigh about 50kg and are usually laid down in sets of two or three. They don’t physically slow vehicles down, but act as a sensory trigger, alerting drivers to changing road conditions ahead. In this trial, the portable rumble strips were placed in 30km/h crossover points, just before drivers were directed into the opposite tunnel lane, and again before they returned to their original alignment.

Image: Rumble strips at the tunnel’s exit alert drivers to changed lanes ahead

How Portable Rumble Strips Were Deployed on SH1

The trial ran over five nights and four days. ASM placed three strips on each end of the closure zone, just before drivers entered and exited the contraflow.

These were high-speed transition zones, reduced from 80km/h to 30km/h. The goal was to trigger driver attention before alignment changes occur.

“We put them at strategic points right before the crossovers. When drivers hit the rumble strips, it snapped them to attention.”

Image: Rumble strips on the road to alert drivers of the lane diversion ahead (source ASM).

Hear From Auckland System Management

Click on the video link below to find out how the ASM team used portable rumble strips to slow traffic, significantly enhancing site safety and efficiency overall.

Credit: Auckland System Management

The Result: Zero Lane Breaches During the Trial

A key KPI for a lane closure is how many vehicles breach the new layout. It is a safety risk for workers and road users that is measured and monitored.

With the rumble strips in place ahead of the lane change, drivers slowed down before the lane crossover point. They stayed in their lane and complied with the diversion, resulting in:

• No road run-offs
• No head-on crashes
• No safety incidents involving crew.

That’s a massive safety and operational win for the client, crews and public road users.

Why ASM Stuck With Rumble Strips After the Trial

Unexpectedly, the crew didn’t want to stop using them.

After the trial, Fiti went looking for the equipment to return it to Vanguard but discovered they had already been repurposed to another site.

“I was supposed to return them, but the crew started using them again for a completely different setup. That says a lot. When teams start using safety gear voluntarily, it’s a good sign it’s working.”

Crews began using the strips in Stop-Go operations. To prompt drivers to reduce speed before reaching the traffic controller, a use outside the original scope. This kind of organic adoption signals authentic, crew-led buy-in.

Technical Challenges: Movement and Minor Damage

Like any new control, the rumble strips were not perfect. ASM identified two issues during the trial:

1. Movement

Despite their weight and grippy surface, the strips occasionally shifted position. Video footage indicates this was likely due to heavy vehicles braking directly on them.

“They didn’t stay exactly where we thought they would. But our teams monitored it, and just repositioned them as needed.”

As long as the site was attended, this wasn’t a major issue.

2. Damage

Two portable rumble strips units came apart, but not due to poor durability. The plastic connector joints (a designed failure point) took the impact, not the strip itself.

“One came apart when a truck and trailer skidded across it and dislodged the joint. The car following behind suffered minor bumper damage.”

Cost and Durability: Are Rumble Strips Worth the Investment?

A set of three portable rumble strips costs approximately $15,000 NZD. ASM used 2 x sets of rumble strips; 1 set at each crossover point

“If they prevent even one incident, it’s worth it. In this case, we had zero.”

If you don’t have the upfront budget, Vanguard Rental offers an operating lease to spread the payments over 6 – 12  months.

The crew’s main concern was durability. Would the rumble strips stand up to heavy vehicles and speeding drivers? After almost a week of use on a live, high-speed closure, the strips proved robust, reusable and easy to repair.

The design feature allowing the plastic connectors to be easily replaced means that repairs can be handled in-house with a pin repair kit:

“We could fix them ourselves with the right parts. That makes it more cost-effective.”

Image: Replacing damaged pins is easy with a pin repair kit.

So, Do Portable Rumble Strips Actually Work?

Yes. And fast.

In one of the most high-risk TTM configurations, contraflow through active tunnels, the portable rumble strips:

• Reduced vehicle speed
• Prevent lane breaches
• Gained crew trust
• Created measurable safety outcomes.

A Proven, Practical Solution for Reducing TTM Site Breaches

Portable rumble strips didn’t just solve a speed problem for ASM, they managed speed by increasing driver attention. This reduced the risk of vehicles driving into a worksite at 80km/h, causing harm to crew and road users.

After trialling portable rumble strips for five nights on SH1 and zero incidents, the ASM team saw PRS as more than a trial: they became a trusted safety tool. When your crew starts redeploying new gear voluntarily, it’s no longer “innovation”, it’s best practice.

The real issue at Johnstone Hill wasn’t signage or TMP compliance. It was speed.

PRS helped bridge that gap. And they did it without major infrastructure, downtime, or disruption.

If you manage crossover points, Stop/Go operations, or any setup where inattention or speed is a factor, this is a tool worth exploring.

Are Portable Rumble Strips Right for Your Worksite?

As ASM have found, this real-world trial of portable rumble strips has mitigated the risk of speeding drivers breaching TTM sites.

If you’re facing a similar challenge on your sites and want to see how portable rumble strips could improve driver attention and reduce speed, get in touch with us to discuss booking a trial so you can see for yourself.