How Kajima Cut Unplanned Work Stoppages by 4 Per Year on a Government Rail Contract

On a fixed-deadline government rail contract, a single unplanned work stoppage does not just cost a day. It triggers contractual notification obligations, disrupts subcontractor schedules, and moves the entire programme. In urban Japan, where the Meteorological Agency issues formal weather warnings that require on-site staff deployment regardless of whether a specific site is actually at risk, the cost of acting on a regional forecast rather than site-specific data compounds quickly.

Kajima Corporation’s Deputy Section Chief Yuki Watanabe manages shaft construction for a major urban underground railway project in Osaka. This is the tool that changed how his team makes wind decisions, and what that change is worth.

Site-specific wind analysis: modelling wind conditions at a construction site based on actual surrounding geometry buildings, structures, and topography, delivering location-accurate forecasts rather than regional averages.

The Problem: Regional Forecasts Create Schedule Risk, Not Just Safety Uncertainty

The project is a new underground railway commissioned by a major Japanese rail operator. Kajima’s shaft construction near a central urban station involves a vertical access point reaching 50 metres below ground, used to launch the tunnel boring machine horizontally beneath the city.

The shaft requires heavy machinery reaching approximately 30 metres above ground. Surrounding buildings reach up to 100 metres tall within a 400-metre radius. That geometry creates localised wind speed spikes between buildings that bear no relationship to what a regional weather forecast reports.

The diaphragm wall construction work made this especially high-stakes. Lowering large reinforcement cages into the ground means large surface areas exposed to wind at height, with precision tolerances that leave no margin for unexpected gusts.

Before ArchiWind Live, the team worked the way most construction sites do: regional weather forecasts, interpreted by experienced crew members. The problem is not expertise. It is what inconsistency costs.

“Experienced workers had to rely on personal intuition to assess risk from forecasts — and that led to significant inconsistency between individuals.” ~ Yuki Watanabe, Deputy Section Chief, Kajima

Over-caution means stopping work when conditions are actually safe, a direct schedule impact on a fixed-deadline contract. Under-caution means continuing when conditions are not, a safety and liability exposure on a public urban site with daily foot traffic nearby. Both outcomes are the predictable result of making site-level decisions with area-level data.

The Solution: The Whole Team Working from the Same Data

The first thing ArchiWind Live changed was not a feature, it was a shared operational picture. Where previously each team member interpreted a regional forecast through their own experience, the team now makes go/no-go decisions in seconds, from data everyone on site trusts.

Kajima adopted ArchiWind Live in April 2024. The platform delivers wind speed and direction forecasts calibrated to the actual site geometry, accounting for surrounding buildings, the shaft configuration, and the changing site layout as construction progresses.

Implementation was direct. A large screen displaying ArchiWind Live was installed in the site office, visible to all staff throughout the working day. Wind conditions became part of the shared operational picture rather than something each individual had to seek out and interpret independently.

How ArchiWind Live Changed Specific Decisions, and What That Means for the Project

Site geometry modelling, not open-terrain averages. ArchiWind Live models the actual built environment surrounding the site. For Kajima, this identified which sections of the perimeter fencing faced the strongest wind exposure, a direct consequence of the surrounding building layout. Fencing was reinforced before events, not after. On a public urban site, shifting from reactive to proactive directly reduces both safety exposure and the cost of emergency remediation.

Hour-by-hour forecasts that protect programme integrity. Knowing wind conditions hour by hour allows the team to adjust working hours and plan crane lift direction and position in advance. For the reinforcement cage work, where surface area and height combine to create maximum wind exposure, this planning capability protects the daily schedule on a contract where delays have contractual consequences.

Shared visibility that removes individual interpretation. The whole team reads the same display. Decisions about whether to proceed, pause, or prepare are no longer subject to variation between crew members. This matters most during high-stress periods, approaching typhoons, sustained wind events, when the cost of a judgement call going wrong is highest.

Proactive response, not reactive scrambling. For sections covered with screening sheets, the team now removes them before risk emerges rather than responding to it.

“Cameras can only show things physically moving, you can’t feel the wind. Combined with ArchiWind Live, we can assess actual wind conditions at each location, understand what is coming, and act. Response time: Instant."~ Yuki Watanabe

The Numbers: €20,473 to €25,862 in Recovered Productivity Per Year

The calculation starts with what Kajima confirmed directly. Under the previous forecast-based approach, the team stopped work as a precaution on approximately four occasions per year when site-specific data later confirmed conditions were safe to continue.

At this site, a strong wind event, including mobilisation, standby, and recovery, requires approximately four workers for three days.

4 stoppages avoided × 4 workers × 3 days = 48 person-days per year

At Osaka construction site day rates (€107.45 to €134.31 per skilled worker per day), direct labour cost avoided is approximately €5,170 to €6,470 annually. Including equipment standby, supervision, subcontractor knock-on costs, and programme recovery overhead, total avoided cost is estimated at €20,473 to €25,862 per year.

The second cost category is less straightforward to pin down to a single number, but equally material for construction directors managing government contracts. In Japan, when the Meteorological Agency issues a formal weather warning, site staff must remain on-site for inspection. Because public transport halts during warnings, staff must travel to the site in advance and wait, regardless of whether the site is actually at risk.

A single unnecessary typhoon standby deployment typically brings 8–12 workers to site for 12–24 hours. At the same day rates, that is €862 to €1,615 per avoidable deployment. ArchiWind Live gives the team the ability to assess whether their specific location will be affected before committing to standby, a direct cost avoidance that repeats with every weather warning issued near the site.

During Typhoon Shanshan in 2024, the team used ArchiWind Live to make four decisions in real time: when to stop work, where to reinforce perimeter fencing, which screening sheets to remove, and when staff needed to be on-site. Each decision was grounded in site-specific forecast data, not a regional weather alert.

What This Means for Urban Construction Projects

This case is a clear example of a pattern that applies across urban construction. When equipment heights, surrounding building geometry, and fixed-deadline programme pressure combine, the gap between a regional forecast and actual site conditions is not a minor inconvenience, it is a direct source of schedule risk and liability exposure.

ArchiWind Live closes that gap by replacing individual interpretation of general forecasts with site-specific, continuously updated wind intelligence shared across the entire team. The productivity recovery, 48 person-days,€20,520 to €25,920 annually, substantially exceeds the cost of the subscription.

“Once you’ve used it, anyone can see it’s already an excellent product."~ Yuki Watanabe, Kajima Corporation