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Traffic heat map of Mercer County, Illinois: 170 miles of roads shaded from blue (light) to red (heavy traffic), busiest on Southeast 3rd Street and 1st Street

Mercer County, Illinois Traffic Counts

Its busiest road, Southeast 3rd Street, carries 7,316 vehicles a day, 3.3 times the average road. This page breaks down traffic in Mercer County, Illinois across 170 miles of monitored roads split into 1,336 segments, using multi-sourced mobile and sensor data. It goes beyond raw counts to truck flow, congestion and who is driving, so site selection and route planning rest on evidence.
Data sourced from TrafficZoom's proprietary analytics platform.
Data current as of:
Q3 2026
Updated:
September 29, 2026
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Total Traffic Volume & Performance in Mercer County, Illinois

Traffic

The average number of vehicles that travel each day over any road in the road network.

vehicles per day2,196
Trucks

The percentage of the total traffic volume composed of heavy vehicles.

9.0%
Average travel time

The average time of travel averaged among all vehicles traveling on the road network.

29.6 min
Congestion ratio

The rate at which the actual travel time exceeds free-flow travel time, averaged among all roads in the network.

8.4%
Drivers’ average age

Average age of residents in the geographic areas where the vehicle trips originated.

51.9 yrs
Drivers’ average income

Average income of residents in the geographic areas where the vehicle trips originated.

$73,340

A typical monitored road in Mercer County, Illinois sees 2,196 vehicles per day, while its 170 miles of monitored roads together handle 299,994 vehicle-miles traveled per day (≈109 million per year). About 1 in 11 vehicles is a truck, in line with Illinois (10.2%).

Shorter trips than 97% of counties in Illinois

Mercer's average daily traffic volume is 74% lower than the state average - 2,196 vehicles per day against 8,480 - suggesting less traffic load per road - very light roads: easy truck access, but little passing trade for roadside retail. In total volume terms, its road network carries about 0.1% of Illinois's statewide total of vehicle-miles. By volume, Mercer's 2,196 vehicles per day trails 80% of counties in Illinois.

At 29.6 minutes, the average travel time is 13% lower than the state level. Its average travel time of 29.6 minutes is shorter than 97% of counties in Illinois.

Congestion runs 59% lower than the state level, at a ratio of 8.4%, which means smoother traffic flow - free-flowing roads make scheduled deliveries highly predictable.

Time-of-Day & Seasonal Patterns

Data Finding: Hourly & Seasonal Patterns

In Mercer County, Illinois, the peak hour concentrates about 7% of the day's traffic.

Mercer County vs. Illinois Traffic Comparison

The average daily traffic per road sets Mercer County apart: 74% below the Illinois average.

MetricMercer CountyIllinois averageDifference
Traffic2,1968,480-74.1%
Truck % (Total Traffic)9.0%10.2%-11.9%
Avg. Travel Time29.6 min34.1 min-13.4%

How Mercer County compares

Mercer County against nearby counties

Against the 4 nearest areas, Mercer County is 31.6% more congested; it has the second busiest roads of the five.

Mercer County and the 4 nearest county-level areas by centroid distance, with the Illinois average for scale.
AreaAverage daily trafficTruck shareDaily vehicle-milesAverage travel timeCongestion ratio
Mercer County2,1969.0%299,99429.6 min8.4%
Warren County, Illinois1,79311.6%500,34232.4 min6.7%
Henderson County, Illinois1,58010.2%252,44933.9 min5.1%
Louisa County, Iowa1,18010.7%238,87438.6 min5.3%
Muscatine County, Iowa2,4998.7%746,54833.6 min8.4%
Illinois average8,48010.2%N/A34.1 min20.6%

Mercer County ranked within Illinois

Mercer County sits in the bottom quarter of the Illinois field on average travel time, at #99 of 102.

Mercer County ranked among 102 county-level areas in Illinois (1 = highest).
MeasureMercer CountyIllinois rank
Traffic volume (AADT)2,196#82 of 102
Average travel time29.6 min#99 of 102
Average driver income$73,340#49 of 102
Average driver age51.9 yrs#16 of 102

The two ends of this table sit far apart: #16 of 102 on average driver age, against #99 of 102 on average travel time.

Busiest roads in Mercer County, Illinois

Traffic concentrates on a few corridors: the three busiest roads average 6,630 vehicles a day, against 2,196 on the average road in Mercer County.

Southeast 3rd Street leads with 7,316 vehicles a day, 422 of them trucks (5.8%). 13th Street carries the most trucks, 514 a day (8.7% of its traffic), although it ranks #3 for all traffic.

Ranked by daily traffic (AADT)

Cars and light vehiclesTrucks
1Southeast 3rd StreetPrimary road · 7,316vehicles422trucks · 5.8%
Road class
Primary road
Congestion ratio
20.2%
Median trip time
28.0 min
Drivers’ median age
52.3 yrs
Drivers’ average income
$69,125

Travel on Southeast 3rd Street's busiest stretch runs 20% over free-flow time, against 8% across the county, so expect slower peak hours.

21st StreetPrimary road · 6,667vehicles507trucks · 7.6%
Road class
Primary road
Congestion ratio
15.9%
Median trip time
30.6 min
Drivers’ median age
51.6 yrs
Drivers’ average income
$80,055

1st Street is one of the more congested roads here: trips take 16% longer than at free-flow speed, against 8% county-wide.

313th StreetPrimary road · 5,908vehicles514trucks · 8.7%
Road class
Primary road
Congestion ratio
14.0%
Median trip time
33.6 min
Drivers’ median age
51.4 yrs
Drivers’ average income
$76,706

The busiest stretch of 13th Street carries 2.7 times the county average; trucks are 8.7% of it, in line with the county-wide 9.0%.

4US 67Primary road · 5,882vehicles504trucks · 8.6%
Road class
Primary road
Congestion ratio
13.1%
Median trip time
33.3 min
Drivers’ median age
51.3 yrs
Drivers’ average income
$78,199

On its busiest stretch, US 67 carries 2.7 times the county average; trucks are 8.6% of it, in line with the county-wide 9.0%.

5Southwest 3rd StreetPrimary road · 5,690vehicles355trucks · 6.2%
Road class
Primary road
Congestion ratio
13.9%
Median trip time
27.2 min
Drivers’ median age
51.8 yrs
Drivers’ average income
$67,054

Southwest 3rd Street peaks at 5,690 vehicles a day, 2.6 times the county average; trucks are 6.2% of it, below the county-wide 9.0%.

Ranked by trucks per day

Cars and light vehiclesTrucks
113th StreetPrimary road · #3 by traffic5,908vehicles514trucks · 8.7%
21st StreetPrimary road · #2 by traffic6,667vehicles507trucks · 7.6%
3US 67Primary road · #4 by traffic5,882vehicles504trucks · 8.6%
4Southeast 3rd StreetPrimary road · #1 by traffic7,316vehicles422trucks · 5.8%
5Southwest 3rd StreetPrimary road · #5 by traffic5,690vehicles355trucks · 6.2%
How to read these road counts
  • The first number is AADT, annual average daily traffic: the vehicles passing a point on an average day, both directions combined and trucks included. On a divided highway both carriageways are added together.
  • Traffic changes along a road, with more near interchanges and towns and less in open country. Every figure for a road describes its busiest stretch in the county, so the two rankings show the same numbers for the same road.
  • The second number is the trucks on that stretch, a part of its AADT. The bar splits the AADT into cars and light vehicles (blue) and trucks (amber).
  • See segment-level AADT for any road on TrafficZoom.

Data Sources & Methodology

The data presented on this page is derived from TrafficZoom's proprietary analytics platform, which aggregates and normalizes information from multiple sources, including:

Mobile device location data (anonymized and aggregated)

Road sensor networks and traffic counters

Historical traffic pattern databases

Public traffic count programs published by the

MercerDepartment of Transportation

Demographic Baseline for O-D Modeling

U.S. Census Bureau
All metrics represent estimates based on statistical modeling and are intended for strategic planning purposes.
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Data current as of:
Q3 2026

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Counties near Mercer County

The same traffic breakdown for the areas closest to Mercer County, Illinois.

Need segment-level traffic data?

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