Speeding is one of the leading causes of serious car accidents in Illinois. Speed limits are not random — they are carefully established using traffic engineering studies designed to reduce crashes and prevent catastrophic injuries. When a driver exceeds a posted or statutory speed limit in Chicago or anywhere in Illinois and causes a collision, that violation may significantly increase their legal liability in a personal injury claim.

At McHargue & Jones, LLC, we represent victims injured in speed-related motor vehicle accidents throughout Chicago and Cook County. If you were injured by a negligent or speeding driver, our Chicago car accident lawyers can evaluate your claim and explain your legal options under Illinois law.

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Quick Summary: Why Speed Limits Matter in Injury Claims

• Speed limits are based on engineering and crash data

• Speeding increases both crash risk and injury severity

• A speeding driver may be considered negligent under Illinois law

• Speeding strengthens liability in many motor vehicle accident cases

• Serious speed-related crashes often result in catastrophic injuries

If you’re unsure how fault works in Illinois, see:
👉 Is Illinois a No-Fault Car Accident State?

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Who Sets Speed Limits?

Speed limits are established and enforced by state and local authorities, including the Illinois Department of Transportation (IDOT). National guidance often comes from the Federal Highway Administration (FHWA), part of the U.S. Department of Transportation.

According to the FHWA’s guidance on speed management:
🔗 https://highways.dot.gov/safety/speed-management

States ultimately implement and enforce these limits based on traffic studies and safety data.

Illinois crash statistics and roadway safety information are also available through:
🔗 Illinois Department of Transportation (IDOT): https://idot.illinois.gov/

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Types of Speed Limits in Illinois

1️⃣ Statutory Speed Limits

Statutory limits are set by state law and apply even when signs are not posted. Drivers are expected to know and follow them.

These often apply to:

• Residential areas

• School zones

• Certain highway categories

Even without signage, drivers may still be cited — and held liable — for violating statutory limits.

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2️⃣ Posted (Regulatory) Speed Limits

Posted speed limits are displayed on roadway signs and are typically determined through traffic engineering studies. These limits may vary significantly depending on:

• Road design

• Traffic volume

• Crash history

• Pedestrian presence

• Surrounding environment

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3️⃣ Special Speed Limits

Special limits apply in temporary or high-risk situations such as:

• Construction zones

• Weather conditions

• School hours

• Public events

• Heavy pedestrian traffic

Speeding in these zones may result in enhanced penalties and stronger negligence arguments in injury claims.

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How Are Speed Limits Actually Determined?

Speed limits are typically established through engineering studies that evaluate multiple safety factors.

Prevailing Speed (85th Percentile Rule)

Engineers study the speed at which 85% of drivers naturally travel under normal conditions. This helps determine a safe and reasonable posted limit.

Roadway Design and Geometry

Factors include:

• Curves and slopes

• Lane width

• Number of lanes

• Visibility and sight distance

• Intersections and merge points

Traffic Volume and Congestion

High-volume roads, such as Chicago expressways and busy Cook County corridors, may require adjusted limits to reduce crash risk.

Pedestrian and Bicycle Activity

Areas with heavy foot traffic, including urban Chicago neighborhoods, may justify reduced limits.

If your accident involved a pedestrian, see:
👉 Do Pedestrians Always Have the Right of Way in Illinois?

Crash History and Safety Data

Crash frequency and severity are major considerations. According to the National Highway Traffic Safety Administration (NHTSA):

🔗 https://www.nhtsa.gov/risky-driving/speeding

Speeding contributes to thousands of fatal crashes nationwide each year.

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Why Speeding Increases Liability in Illinois Car Accident Claims

Under Illinois personal injury law, drivers have a duty to operate their vehicles safely. Exceeding the posted speed limit — or driving too fast for conditions — may constitute negligence.

Speeding:

• Reduces reaction time

• Increases stopping distance

• Increases force of impact

• Worsens injury severity

When speeding contributes to a crash, it can significantly strengthen an injured victim’s claim for damages.

Illinois follows a modified comparative negligence system (the “51% rule”). Learn more here:
👉 Illinois At-Fault Car Accident Law

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Speed-Related Crashes Often Cause Severe Injuries

High-speed collisions frequently result in:

• Traumatic brain injuries

• Spinal cord injuries

• Multiple fractures

• Internal bleeding

• Permanent disability

Learn more about life-altering trauma here:
👉 Catastrophic Injuries After Auto Accidents

Speeding is especially dangerous in:

• Rear-end accidents

• Drunk driving accidents

• Distracted driving crashes

• Commercial vehicle and truck accidents

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How Do You Prove a Driver Was Speeding?

Insurance companies often deny allegations of speeding unless evidence is strong.

Evidence may include:

• Police accident reports

• Traffic camera footage

• Dashcam recordings

• Eyewitness statements

• Skid mark measurements

• Vehicle damage analysis

• Accident reconstruction expert testimony

In serious motor vehicle accident cases, expert witnesses may be necessary to establish both liability and future damages.

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Insurance Policy Limits in Speeding Cases

Even when speeding clearly caused a crash, compensation may depend on available insurance coverage.

Illinois minimum auto insurance is typically:

• $25,000 per person

• $50,000 per accident

In catastrophic injury cases, these limits may be exhausted quickly.

Victims may need to explore:

• Underinsured motorist (UIM) coverage

• Uninsured motorist (UM) coverage

• MedPay coverage

• Umbrella policies

• Third-party liability

If the crash involved a commercial truck, significantly higher policy limits may apply. See:
👉 Truck Accident Claims in Illinois

For broader legal guidance, visit:
👉 Illinois Personal Injury Lawyers

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What to Do After a Speeding-Related Car Accident in Chicago

If you were injured in a speed-related traffic collision:

1. Call 911 and request a police report

2. Seek immediate medical treatment

3. Photograph skid marks, vehicle damage, and road conditions

4. Obtain witness contact information

5. Avoid recorded statements to insurance adjusters

6. Preserve all medical and wage documentation

7. Consult with a car accident attorney before accepting a settlement

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Frequently Asked Questions About Speed Limits and Car Accident Liability

How are speed limits determined?

Speed limits are determined through traffic engineering studies that evaluate prevailing speed, road design, crash history, pedestrian activity, and traffic volume.

Is speeding considered negligence in Illinois?

Speeding may be considered evidence of negligence if it contributed to the crash or increased injury severity.

Can I sue a speeding driver in Illinois?

Yes. If a speeding driver caused your injuries, you may pursue compensation through an insurance claim or lawsuit under Illinois personal injury law.

Does speeding increase a car accident settlement?

It can. Evidence of speeding may strengthen liability and increase potential compensation, especially in serious injury cases.

What if the speeding driver only has minimum insurance?

Recovery may be limited unless additional insurance coverage applies, such as underinsured motorist coverage or umbrella policies.

Are speeding truck accidents handled differently?

Yes. Truck accidents often involve commercial insurance policies, corporate defendants, and higher liability limits.

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Injured by a Speeding Driver in Chicago?

Speed-related crashes often cause devastating injuries and complex insurance disputes. At McHargue & Jones, LLC, we represent victims of serious motor vehicle accidents throughout Chicago and Illinois.

If you were injured in a speeding collision, contact our office for a free consultation.

📞 Call (312) 739-0000

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Disclaimer: This article is for informational purposes only and does not constitute legal advice.