You find a great site on a busy road. The spot looks perfect for your project. Then the city asks for a traffic study before they will sign off. A traffic study looks at how your project will change traffic on the roads around it. On a busy corridor, this one step can shape your whole schedule. It can add weeks if you wait too long. It can save weeks if you plan ahead. Here is what these studies ask for, why they matter, and how to stay in front of them.
What a traffic study checks
A traffic study measures how many cars your project adds to nearby roads. It also checks if those roads can handle the extra load. Engineers count the traffic that is on the road now. They estimate the new trips your site will make. Then they see how the two mix at driveways and intersections.
The goal is simple. Keep traffic safe and moving after your project opens. If the roads cannot take the added cars, the study shows what fixes are needed and where. That way, no one is surprised later.
When a busy corridor triggers a study
Not every project needs one. But busy corridors raise the bar fast.
Most cities set a trip threshold. When your project is expected to add more than a set number of peak hour trips, a study kicks in. Many agencies use around 100 new peak hour trips as the line, though the exact number changes by place. Always check the local rule first.
Other things can trigger a study too:
- A new driveway or road connection on a busy street
- A rezoning request that changes how the property can be used
- A land use change that increases expected traffic
- A project near a crash-prone intersection
- A site that needs a new or changed traffic signal
On a quiet street, a small shop may slip by with no study. On a packed corridor, the same shop may need a full review. The road, not just the project, drives the call.
What goes inside the study
A study has a few main parts. Each part answers a question the city will ask.
Trip generation
This part estimates how many car trips your site will make. Engineers use trip rates tied to your land use, like a shop, office or apartment. More units or more floor space mean more trips. A busy drive-thru makes far more trips than a quiet warehouse of the same size.
Traffic counts
Engineers count real traffic on the roads by your site. They focus on peak hours, like the morning and evening rush. These counts show how busy the road already is before you add a single car. Counts are the base for the whole study, so they need to be fresh and accurate.
Intersection and driveway review
The study checks how cars will move in and out of your site. It looks at wait times, turn lanes and sight lines. Can drivers see far enough when they pull out? Will cars stack up and block the road? Busy corridors often need a left turn lane or a signal to keep drivers safe.
Safety check
Engineers review crash history on the corridor. If a spot already sees a lot of crashes, your project cannot make it worse. The study may call for better driveway spacing or a safer entrance. Safety often carries more weight than delay when a city reviews your plan.
Why busy corridors get extra care
Busy roads have little room to spare. One small change can back up a long line of cars. Cities know this. So they ask harder questions when a corridor already runs near its limit.
A study on a busy corridor may need more count spots. It may cover more intersections than a study on a slow street. It may also model traffic a few years out to plan for growth. The city wants to know the road still works once other nearby projects open too. All of this takes more time, so build that time into your plan from day one.
How to plan ahead
You can save weeks by starting early. Here is how.
- Ask about traffic rules before you buy. Call the local traffic or public works office.
- Bring a traffic engineer onto your team at the start, not after plans are drawn.
- Order traffic counts early. Counts often cannot run on holidays or school breaks.
- Budget for road fixes. A turn lane or signal can cost real money.
- Leave room in your site plan for a wider entrance or a turn lane.
A little planning up front keeps the study from stalling your project later. Skip this step, and a late fix can force a full redesign.
The payoff
A traffic study can feel like a hurdle. It is really a shield. It shows the city your site works. It lowers the risk of a costly redesign. It helps your building open on time.
Treat the study as a tool, not a tax. Plan for it early, and it moves fast. Ignore it, and it can hold up everything else.
Frequently Asked Questions
How long does a traffic study take?
Most traffic studies take four to eight weeks. Projects along busy corridors may take longer. The schedule also depends on when traffic counts can be collected and how quickly the local agency reviews the completed report.
Who pays for the traffic study?
In most cases, the developer pays for the traffic study. The developer hires a qualified traffic engineer to prepare the report, while the city or reviewing agency evaluates it as part of the development approval process.
Do small projects need a traffic study?
Sometimes. A small project on a low-volume street may not require one, while the same project on a busy roadway could. Local trip-generation thresholds and municipal requirements determine whether a study is needed.
What if the study finds a problem?
If the study identifies traffic concerns, it will recommend improvements. These may include adding a turn lane, installing a traffic signal, modifying driveway access, or making other roadway changes. Depending on local policies, the cost may be shared among the developer, the municipality, or nearby developments.
Can I start design before the study is done?
Yes, but it carries some risk. If the traffic study recommends roadway or access changes, you may need to revise your site plan. Completing the study early helps reduce redesign costs and project delays.