Driveway Traffic Study: Required for Commercial Properties

What a Driveway Traffic Study Really Is (and Why It Matters to You)

A Driveway Traffic Study is a data-driven report that measures how many vehicles enter and exit a property, when they do it, and how those movements affect public roads. Cities usually demand one before they’ll issue a commercial building permit or approve a change of use—say, turning your home-based bakery into a retail storefront or adding a day-care center.

Even if your project is still “just an idea,” understanding the study now will save you surprises, delays, and redesign costs later.

Do Homeowners Ever Need a Driveway Traffic Study?

Typical Triggers for a Study

• Creating a home occupation that brings more than about 10 daily customer trips (thresholds vary by city).
• Building an accessory dwelling unit (ADU) that will be rented or used as an office.
• Adding a second driveway or widening an existing one to more than 12–16 ft.
• Subdividing the lot so each new parcel gets its own curb cut.

How to Check Your Local Rule

Call the municipal “Transportation” or “Development Services” desk and ask for the “trip generation threshold” for residential properties. Anything below that number usually means you can skip the full study and file a simple statement instead.

How a Driveway Traffic Study Works, Step by Step

Step 1: Scoping Meeting

The traffic engineer meets with city staff to confirm study limits, peak hours, and any special conditions (school zones, bus stops, sight-distance obstructions).

Step 2: Data Collection

Counters or video cameras record traffic for at least two typical weekdays and one Saturday. Morning (7–9 a.m.) and afternoon (4–6 p.m.) peak hours are isolated.

Step 3: Trip Generation & Distribution

The raw counts are converted into “passenger-car equivalents” using Institute of Transportation Engineers (ITE) formulas. The engineer then estimates what share of those trips will use each adjacent roadway.

Step 4: Impact Analysis

Existing traffic, background growth, and your project’s new trips are combined. If the total pushes an intersection above the city’s “level of service” standard (usually LOS C or D), mitigation is required.

Step 5: Report & Recommendations

The final document includes a site plan, trip summary tables, crash history, and any proposed fixes—turn-lane additions, signal timing tweaks, or on-site stacking lanes.

What a Driveway Traffic Study Costs—and How to Control It

Ballpark Numbers

• Small residential conversion: $2,500–$4,500
• Mid-size retail pad: $5,000–$9,000
• Complex site with multiple driveways: $10,000–$25,000

Money-Saving Tips

1. Bundle studies. If neighbors are also developing, share the baseline traffic counts.
2. Use city data. Many counties already have 24-hour tube counts you can buy for $50 instead of paying $800 for new ones.
3. Limit scope. Ask whether a “letter of trip generation” satisfies the planner; sometimes that one-page letter costs under $1,000.

Picking the Right Traffic Engineer

Must-Have Credentials

• Professional Engineer (PE) license in your state
• Membership in ITE or equivalent
• Recent city approvals on similar projects (ask for reference letters)

Red Flags

Be wary of bids that are 30 % lower than everyone else—corners get cut on count duration or analysis detail, and the city will send it back.

Timeline: How Long Does Everything Take?

From handshake to stamped report, plan on 4–6 weeks:

• Week 1: Scoping & proposal
• Week 2: Field counts (minimum 3 days)
• Week 3: Data crunching & draft report
• Week 4: City review & revisions
• Weeks 5–6: Final stamp, possible follow-up meeting

Busy summer construction season can add two extra weeks, so book early.

DIY Data Collection: What You Can (and Can’t) Do Yourself

What Homeowners Can Handle

• Manual tally sheets during your own peak times—great for estimating rough trip counts.
• Smartphone time-lapse from an upstairs window—useful for spotting queue spillback.

What You Must Leave to Pros

Calibration of counters, statistical adjustments, and any data that will be entered into city traffic models require a licensed engineer’s seal.

Common Mitigation Measures (and How to Negotiate Them)

On-Site Fixes

• 20-ft stacking lane so cars don’t block the sidewalk
• Dual left-turn lanes if your driveway feeds a major arterial
• Raised median to prohibit risky left turns

Off-Site Fixes

You may be asked to pay a “fair-share” contribution toward a future traffic signal. Cap your exposure by asking the city for a phased reimbursement schedule tied to actual occupancy permits.

Permits & Paperwork: Keeping the Process Moving

Checklist Before You Submit

1. Site plan showing driveway radius, slope, and clear sight triangles
2. Driveway Traffic Study (two bound copies + PDF)
3. Storm-water drainage letter (some cities bundle reviews)
4. Neighborhood notification postcards (required in many jurisdictions)

Typical Review Stages

Administrative → Technical (traffic engineer) → Public hearing (if variances are needed). Respond to comments within 10 business days to avoid going to the back of the line.

How to Increase Approval Odds on the First Try

• Meet neighbors early. A petition with three signatures in support can sway planning boards.
• Schedule counts during school sessions, not holiday weeks, or the city will make you redo them.
• Overlay bike-lane and pedestrian data. Showing awareness of all road users reassures reviewers.

Frequently Asked Questions