The Difference Between Roadblocks & Constraints

Here’s the deal. Maybe I am the last person on the bus with this, but I have never really seen the genius of it until now, and I have been doing and researching Takt for a long time. Everything on our construction project should be organized as trains of trades moving through zones. Once you see it that way, the difference between a constraint and a roadblock becomes the most important distinction in the system.

Short answer: A constraint is part of the design of your train of trades: zone size, Takt time, work packaging, sequence, crew size, or the number of zones. Constraints are permanent or semi-permanent, so you adjust them. A roadblock sits on the tracks ahead of the train, like an unanswered RFI, missing material, or layout that isn’t ready. Roadblocks are temporary, so you remove them.

The Train and the Tracks

The train is going to flow if it is going to a predetermined location, the milestone in the master plan. All of the train and its cars are going in the same direction, in the same sequence. Each of the cars is the same distance apart. The cars are adding the same amount of value, going over the same amount of work per zone along the train tracks, and the train is going the same speed.

The train and its cars are the train of trades. Each Takt wagon is a grouping of one or multiple trades. That is how you get flow in construction, by organizing it this way.

Most of the time, we are only looking five feet ahead of the train, and we are never looking back. But if you have the Takt Production System, now you can see the train. If you have the Last Planner® System, now you can see the tracks.

What Is the Difference Between a Constraint and a Roadblock?

Constraints are items that are part of the design of the train of trades, and they can be adjusted. Roadblocks are items to be cleared ahead of the train of trades. Some people will not agree with me, but I have done a lot of research and a lot of thought on this. I have a blog post coming out on the Lean Builder blog that explains it in detail, and I also did a LinkedIn post. You can reach out to me and I will share the information.

If we do not know the difference, we are not going to be as successful as we can be. Constraints are always there. We cannot entirely remove them. We simply need to adjust them. Roadblocks always need to be removed, and they are always temporary. Constraints are permanent or semi-permanent. Roadblocks are very temporary.

That is why it is important to use the proper wording. It signals different actions from the project team, and that is crucial.

Which Constraints Should You Adjust?

If you have a train of trades going in the same direction, in the same sequence, adding the same amount of value, doing the same amount of work, at the same speed, the same distance apart, these are the things you adjust. And if you do not adjust them, you could bring a demigod, the best people on earth, to do the work, and they still will not go any faster.

• Takt zones. Adjust them so each zone has an equal amount of work, so trades can flow from zone to zone to zone. If one zone has more work than another, you are constrained by it, and it will slow you down.
• Takt time. If you have an improper Takt time or an improper duration, with too much or too little buffer for the Takt wagons, that is a constraint. You want the right Takt time to get the right throughput time for your overall phase, so each wagon and trade has the exact amount of buffer.
• Work packaging. Each crew should have an equal, leveled amount of work, value add, or energy in each zone. If one trade has ten units of work and the next trade partner has twenty-five, that is your bottleneck trade, your slowest trade, and your whole project will only go as fast as that trade.
• The sequence. Sometimes the sequence of the train cars, the trades themselves, creates a constraint. In some buildings you have to adjust the sequence and come in and do priority walls first, so that when the duct goes up you do not have to come back and get the interstitial drywall in. Then you do the overhead, then the wall.
• Labor counts and crew composition. Sometimes you have to split crews apart, supervise two crews, and have them go one in front and one behind.
• Trade processes. Adjust the process so it fits within the sequence and the Takt time in the area.
• Zone configuration. Configure zones around constraints like an elevator, a lobby, the exterior, or an access zone, so the train can flow without the stops and starts that come from permanent logistical fixtures.
• The number of zones. This is crucial. Because of Little’s Law, the number of zones has a lot to do with how fast you go.
• Labor productivity, variation, and the rest. Increase labor productivity by increasing capability, reduce variation by observing and removing it, align the plan for better one-piece flow so nothing is batched, improve standard work, adjust the site configuration to support flow, and mine for unforeseen conditions so they do not become constraints.

On the number of zones, you can parse out a project into equal pieces of ten thousand square feet and say that is your zoning, but that is not actually the best way to do it. You might have five zones, and if you go to six, seven, eight, or nine zones, you will save thirty days, forty-five days, or even a hundred days, because smaller zones produce faster work, up to a point of diminishing return. But if we do not adjust the number of zones, nothing you do will make that train go faster.

Inspect Your Train

It is like being a train conductor who has never done an inspection of the train. You are just sitting up there looking five feet in front of you, hoping everything goes well. You are not looking back at how your cars are functioning. You did not look at how they were loaded, or whether they were balanced, or whether everything was coupled, greased, and maintained.

If you are looking for constraints, you are acting as the train conductor or the engineer, monitoring your train to make sure it is going as fast as it can. You can clear the tracks all you want, but if the train can only go a certain speed, there is nothing you can do to push it.

Which Roadblocks Should You Remove?

Roadblocks are items that can be cleared ahead of the train of trades on the tracks. The train is part of the system design. Roadblocks are the things sitting on the tracks, and clearing them is roadblock removal. Most of these are self-explanatory.

• RFIs that are not answered.
• Layout that is not ready or is incorrect.
• A work area that has not been made ready because of whatever conditions, which you can foresee and clear out ahead.
• Missing material or equipment, which you can track and clear out ahead.
• A crew that is not ready ahead of you. If you use zone control, you can clear that out ahead.
• Improper planning from overcommitment, miscommunication, a change in the work plan, or safety concerns, which are mostly things you can see and clear out ahead.
• An improper sequence, resources that are not available, or work that is not authorized out ahead.
• A change in the work plan by the owner. That one may or may not be controllable, because sometimes they surprise you with it.
• A bunk of plywood in my way, work that is not done, permissions we do not have, an inspector you did not call, or equipment that has not been ordered.

Here are some ways to get roadblocks out of your trade partners early.

These are things that should be cleared from the tracks, and they are always removed.

Seeing a Mile Ahead

If we are ever going to adopt Takt, we have to visualize the train and the tracks. We have to understand that the train and the tracks are where the constraints live, and that roadblocks are the clearing of those tracks out ahead of the train.

If you have implemented the Takt Production System and you are looking for constraints and adjusting them, you are monitoring your train. It is like having a video camera in the front car, the engine, where you can see every part of the train and optimize it for the best speed. And if you have the Last Planner® System with your trade foremen, looking out ahead on your six-week make-ready lookahead plan, you can see roadblocks out ahead. Instead of looking out five feet, you are looking out a mile, making sure the train is clear.

You cannot operate a train of trades, and you cannot flow in construction, if you cannot see the train and see out ahead, if you are not managing constraints, and if you are not managing roadblocks.

To go deeper, see Takt Steering & Control or the Takt Production System Masterclass.

So here is the challenge. Let’s get in the habit. Visualize the train and the tracks, adjust your constraints, and clear your roadblocks.

Bottom line: Constraints get adjusted. Roadblocks get removed.

If your project needs superintendent coaching, project support, or leadership development, Elevate Construction can help your field teams stabilize, schedule, and flow.

Want your team trained on this? See our Last Planner® System and Takt training.

On we go.

FAQ

What is the difference between a constraint and a roadblock?

A constraint is part of the design of the train of trades and can be adjusted but never entirely removed. A roadblock is an item to be cleared ahead of the train on the tracks. Constraints are permanent or semi-permanent, and roadblocks are very temporary.

Why does the number of zones matter?

Because of Little’s Law, smaller zones produce faster work, up to a point. Splitting a project into six, seven, eight, or nine zones instead of five can save thirty, forty-five, or even a hundred days, although there is a point of diminishing return.

What is a bottleneck trade?

The trade with the most work in the leveled sequence. If one trade has ten units of work and the next has twenty-five, the second is the bottleneck, and the whole project only goes as fast as that slowest trade.

What do the Takt Production System and the Last Planner® System each let you see?

The Takt Production System lets you see the train and manage constraints. The Last Planner® System, with the six-week make-ready lookahead, lets you see the tracks and the roadblocks out ahead.

People Also Read:

How Foremen Identify Constraints & Remove Roadblocks in Lean Construction
Last Planner in Construction | Constraints vs Roadblocks (Make-Ready Done Right)
Roadblock Tracking Maps