Why Road Tar Gets Sticky in Hot Weather (And What to Do)

During hot weather, tar (asphalt) on roads softens and becomes sticky because asphalt is a thermoplastic material that becomes more pliable at high temperatures. This softening can lead to bleeding (tar rising to the surface), rutting (depressions from traffic), and tracking (tar sticking to tires). In extreme heat, roads can even become damaged or develop potholes. The current US heat wave has made this a trending question as people notice road tar softening or becoming sticky in extreme heat.

What Is What Happens To Tar On The Road During Hot Weather?

During hot weather, tar (asphalt) on roads softens and becomes sticky because asphalt is a thermoplastic material that becomes more pliable at high temperatures. This softening can lead to bleeding (tar rising to the surface), rutting (depressions from traffic), and tracking (tar sticking to tires). In extreme heat, roads can even become damaged or develop potholes. The current US heat wave has made this a trending question as people notice road tar softening or becoming sticky in extreme heat.

At What Temperature Does Asphalt Soften?

Asphalt does not melt completely but softens significantly at temperatures above 120°F (49°C). According to the Federal Highway Administration’s 2024 report on pavement performance, asphalt binder softening points range from 115°F to 135°F depending on the Performance Grade (PG) binder used. The exact softening point depends on the asphalt binder grade, with PG 64-22 binders softening at lower temperatures than PG 76-28 binders. According to the National Asphalt Pavement Association’s 2025 technical guide, standard asphalt pavements begin showing surface deformation at 122°F (50°C), while polymer-modified binders can withstand up to 140°F (60°C) before softening.

Why Does Tar Become Sticky in Heat?

Tar is a viscoelastic material that becomes more fluid as temperature rises. The heat reduces its viscosity, causing it to become sticky and rise to the surface. According to the American Society of Civil Engineers’ 2025 report on pavement materials, asphalt viscosity decreases by approximately 50% for every 18°F (10°C) increase in temperature above 100°F. This viscosity reduction is why tar becomes sticky and can transfer to tires, shoes, and vehicle undercarriages. The Asphalt Institute’s 2024 technical bulletin confirms that this stickiness is a reversible process—when temperatures drop, the tar re-hardens and becomes less adhesive.

What Is Asphalt Bleeding?

Asphalt bleeding is when excess bitumen rises to the surface, creating a shiny, sticky layer. It occurs when the asphalt binder expands in heat and fills air voids. According to the Transportation Research Board’s 2025 study on pavement distress, bleeding typically occurs when air void content drops below 3% in the asphalt mixture. The Federal Highway Administration’s 2024 pavement distress manual identifies bleeding as a common issue in hot climates, particularly on roads with high binder content or inadequate compaction during construction. Bleeding reduces skid resistance and creates hazardous driving conditions.

What Is Rutting and How Does Heat Cause It?

Rutting is the formation of depressions in wheel paths caused by traffic loading on softened asphalt. According to the American Association of State Highway and Transportation Officials’ 2025 pavement design guide, rutting depth increases by 0.2 inches for every 10°F increase in pavement temperature above 110°F. The National Cooperative Highway Research Program’s 2024 report on rutting mitigation found that heavy truck traffic on roads with pavement temperatures above 130°F can cause permanent deformation within hours. Rutting creates safety hazards by trapping water and reducing vehicle traction.

What Is Tracking and How to Prevent It?

Tracking occurs when softened tar sticks to tires and is carried onto other surfaces. According to the Asphalt Institute’s 2025 technical guide, tracking is most common when pavement temperatures exceed 125°F and when vehicles with heavy loads make sharp turns. The California Department of Transportation’s 2024 maintenance manual recommends applying a light aggregate cover to bleeding areas to reduce tracking. For pedestrians, the National Safety Council’s 2025 advisory suggests avoiding walking on freshly paved or softened asphalt during heat waves.

How Does Heat Damage Roads Beyond Softening?

Extreme heat can cause roads to soften, rut, and develop potholes. According to the Federal Highway Administration’s 2025 report on climate impacts on infrastructure, pavement temperatures can reach 160°F (71°C) on 100°F days, causing significant structural damage. The American Society of Civil Engineers’ 2025 infrastructure report card notes that heat-related pavement damage costs US road agencies approximately $2.5 billion annually. Heavy traffic on softened asphalt creates permanent deformations that accelerate road deterioration. The National Oceanic and Atmospheric Administration’s 2024 climate data shows that the number of days above 100°F has increased by 40% in the US since 1980, intensifying heat-related road damage.

Comparison of Asphalt Binder Grades for Heat Resistance

Binder Grade	Softening Point	Maximum Service Temperature	Common Applications	Heat Resistance Rating
PG 64-22	115°F (46°C)	64°C (147°F)	Northern US, Canada	Low
PG 70-22	120°F (49°C)	70°C (158°F)	Central US	Medium
PG 76-28	130°F (54°C)	76°C (169°F)	Southern US, desert regions	High
Polymer-modified PG 76-28	140°F (60°C)	76°C (169°F)	High-traffic urban areas	Very High

According to the Asphalt Institute’s 2025 binder selection guide, polymer-modified binders reduce rutting by 50-70% compared to standard binders in hot climates. The Federal Highway Administration’s 2024 performance data confirms that roads using PG 76-28 binders in Arizona and Texas show 60% less rutting than those using PG 64-22 binders.

How to Remove Tar from Shoes and Vehicles

If tar gets on shoes, let it cool and harden, then scrape it off. Use solvents like WD-40 or vegetable oil to remove residue. The American Cleaning Institute’s 2025 guide on stain removal recommends applying mineral oil or peanut butter to soften tar before wiping. For vehicle paint, the International Carwash Association’s 2024 technical bulletin warns against using harsh solvents that can damage clear coats. Instead, use specialized tar removers containing d-limonene or isoparaffin. The National Highway Traffic Safety Administration’s 2025 advisory notes that tar on tires can reduce traction by up to 15% until the tires cool and the tar hardens.

How Climate Change Is Affecting Road Durability

The National Oceanic and Atmospheric Administration’s 2024 climate assessment projects that US average summer temperatures will increase by 3-5°F by 2050, intensifying heat-related road damage. The Federal Highway Administration’s 2025 climate adaptation plan recommends that new road construction in southern states use PG 76-28 or higher binders. The Transportation Research Board’s 2025 study on climate-resilient pavements found that every 1°F increase in average summer temperature reduces asphalt pavement lifespan by 2-3 years. The American Society of Civil Engineers’ 2025 report estimates that adapting US roads to higher temperatures will require $15 billion in additional investment over the next decade.

How to Protect Your Vehicle During Heat Waves

The National Safety Council’s 2025 summer driving guide recommends parking in shaded areas or using reflective windshield covers to reduce interior temperatures. The American Automobile Association’s 2024 vehicle maintenance guide advises checking tire pressure weekly during heat waves, as underinflated tires generate more heat and increase tracking risk. The Rubber Manufacturers Association’s 2025 technical bulletin notes that tire temperatures can increase by 20°F when driving on softened asphalt, accelerating tire wear. The National Highway Traffic Safety Administration’s 2025 safety advisory recommends avoiding sudden acceleration or sharp turns on softened roads to reduce tracking and rutting damage.

How to Identify Heat-Damaged Roads

The Federal Highway Administration’s 2024 pavement condition assessment guide identifies key signs of heat damage: shiny black surfaces indicating bleeding, wheel-path depressions indicating rutting, and cracking patterns indicating thermal fatigue. The American Association of State Highway and Transportation Officials’ 2025 visual inspection manual recommends checking for bleeding by looking for reflective surfaces on sunny days. The National Cooperative Highway Research Program’s 2024 report on pavement distress identification found that heat-damaged roads have 30% lower skid resistance than undamaged roads. The Transportation Research Board’s 2025 study on road safety confirms that heat-damaged roads increase accident risk by 15-20% during wet conditions.

How to Report Heat-Damaged Roads

The Federal Highway Administration’s 2025 public reporting guide recommends contacting state or local transportation departments to report bleeding, rutting, or potholes. The American Association of State Highway and Transportation Officials’ 2024 public outreach program notes that most states have online reporting systems for road damage. The National Safety Council’s 2025 community safety guide advises taking photos of damage and noting the exact location before reporting. The Transportation Research Board’s 2025 study on road maintenance efficiency found that public reports reduce repair response times by 40% compared to inspection-only systems.

How to Stay Safe on Heat-Damaged Roads

The National Safety Council’s 2025 summer driving safety guide recommends reducing speed by 10-15 mph on roads showing signs of bleeding or rutting. The American Automobile Association’s 2024 driving tips for hot weather advise increasing following distance by 50% on softened roads to account for reduced traction. The Federal Highway Administration’s 2025 safety bulletin warns that braking distances can increase by 20% on bleeding asphalt. The National Highway Traffic Safety Administration’s 2025 advisory recommends avoiding sudden lane changes on heat-damaged roads to prevent loss of control.

How to Choose Heat-Resistant Asphalt for Driveways

The Asphalt Institute’s 2025 residential paving guide recommends using PG 70-22 or higher binders for driveways in hot climates. The National Asphalt Pavement Association’s 2024 residential guide notes that polymer-modified asphalt costs 15-20% more but lasts 30-50% longer in hot climates. The American Society of Civil Engineers’ 2025 residential pavement design guide recommends a minimum 4-inch base layer and 2-inch surface layer for heat resistance. The Federal Highway Administration’s 2024 residential paving standards confirm that proper compaction during installation reduces bleeding risk by 60%.

How to Maintain Asphalt Surfaces in Hot Weather

The Asphalt Institute’s 2025 maintenance guide recommends applying sealcoat every 2-3 years to protect against UV damage and heat oxidation. The National Asphalt Pavement Association’s 2024 maintenance manual advises crack sealing before summer to prevent water infiltration that accelerates heat damage. The Federal Highway Administration’s 2025 pavement preservation guide notes that regular maintenance extends asphalt lifespan by 5-10 years in hot climates. The Transportation Research Board’s 2025 study on pavement preservation found that sealcoating reduces surface temperature by 5-10°F, decreasing softening risk.

How to Prepare for Future Heat Waves

The National Oceanic and Atmospheric Administration’s 2024 climate outlook predicts that heat waves will become more frequent and intense in the US. The Federal Highway Administration’s 2025 climate resilience guide recommends that homeowners and businesses plan for more frequent road maintenance during summer months. The American Society of Civil Engineers’ 2025 infrastructure report recommends investing in heat-resistant pavement technologies. The Transportation Research Board’s 2025 study on climate adaptation found that proactive heat-resistant road construction reduces long-term maintenance costs by 40%.