Aeroscreen
A windscreen-style canopy fitted over the cockpit to protect a driver's head from debris and impacts. It is IndyCar's equivalent of the halo device used in Formula 1, though structurally different — a titanium frame supporting a ballistic-resistant polycarbonate screen, rather than an open bar structure.
It was introduced following a series of serious head-injury incidents and now sits over every car on the grid, regardless of circuit type.
Push-to-Pass
A driver-activated system that adds roughly 60 extra horsepower for a limited, budgeted amount of time per race. It is only used on road and street courses, not ovals, and managing the fixed allocation across a race is a genuine strategic skill.
Read our full explainer on push-to-pass and the hybrid ESS for the exact time budgets and how the rules have changed.
Hybrid ESS
The Energy Storage System introduced in July 2024: a 48-volt motor-generator unit and 20 supercapacitors packaged in the bellhousing, capturing energy under braking for another roughly 60 horsepower on demand. Unlike push-to-pass, it works on every circuit type, including ovals, and recharges fully in about 4.5 seconds of braking rather than running down a fixed race-long budget.
Stacked with push-to-pass on a road or street course, the two systems together can push a car's output past 800 horsepower.
Pit Window
The range of laps within which a team can reasonably make a pit stop given fuel range and tire wear, without running out of fuel or losing excessive time on worn tires before the stop.
Strategy often revolves around choosing exactly when within that window to pit — early to react to a caution period, or late to gain a fresher-tire advantage right before the end of a stint.
Caution Period and Yellow Flag
A caution period is called when an incident — a crash, debris, or standing water — makes racing unsafe at full speed. Cars slow to a controlled pace behind a pace car, and the field typically bunches back up.
Cautions are pivotal to IndyCar strategy: teams frequently pit during a caution period because the cost of a stop, measured in lost track position, is much lower when the whole field is running slowly anyway.
Double-File Restart
When racing resumes after a caution period, cars restart in two side-by-side rows rather than a single file, which produces close, contested restarts and is frequently where overtaking on ovals is concentrated.
Restarts are a common flashpoint for incidents precisely because cars are close together and the field is accelerating simultaneously from a relatively low speed.
Spec Chassis
Every team races an identical Dallara chassis rather than a car of its own design. Teams differentiate themselves through their choice between two approved engine suppliers (Honda or Chevrolet), setup work, strategy and driving rather than through unique aerodynamic or structural design.
This is the single biggest structural difference between IndyCar and development-based series such as Formula 1 — see our full IndyCar vs F1 comparison for what that produces on track.
Oval Kit and Road/Street Kit
IndyCar's one spec chassis actually runs two genuinely different aerodynamic configurations depending on circuit type. The oval kit uses a tiny rear wing, minimal front wing and a smooth underbody to minimize drag for 230mph-plus speeds. The road/street kit swaps in much larger wings front and rear, trading that top speed for the downforce needed to actually corner on a twistier track.
No other major single-seater series maintains two such different packages for the same car, because none of the others race on ovals at all.
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Frequently asked questions
What is an aeroscreen in IndyCar?
A windscreen-style canopy made of a titanium frame and ballistic-resistant polycarbonate that protects a driver's head from debris. It is IndyCar's equivalent of Formula 1's halo device.
What does pit window mean in IndyCar?
The range of laps during which a team can reasonably make a pit stop given fuel range and tire wear, without running out of fuel or racing too long on worn tires beforehand.
What is a caution period?
A period where cars slow to a controlled pace behind a pace car because an incident has made full-speed racing unsafe. Teams frequently use cautions to pit at a lower strategic cost.
What is a double-file restart?
A restart after a caution period where cars line up two-by-two rather than in a single file, producing close, contested restarts that are a common site of overtaking and incidents.
What does spec chassis mean?
Every IndyCar team races an identical Dallara chassis. Teams differentiate through engine supplier choice, setup, strategy and driving rather than unique car design.
Is the aeroscreen the same as F1's halo?
They serve the same purpose — protecting a driver's head in an open cockpit — but are structurally different. The aeroscreen is a full transparent screen on a titanium frame, while the halo is an open bar structure.
What is push-to-pass in one sentence?
A driver-activated system adding roughly 60 horsepower for a limited, budgeted time per race, used only on road and street courses.
What is the hybrid ESS in one sentence?
A 2024-introduced energy-recovery system adding roughly 60 horsepower on demand, recharging from braking in about 4.5 seconds, and available on every circuit type including ovals.
What's the difference between the oval kit and the road/street kit?
The oval kit runs tiny wings and a smooth underbody to minimize drag for high top speed. The road/street kit runs much larger wings to maximize downforce and cornering grip, at the cost of top speed.
How much combined horsepower can an IndyCar produce?
Over 800 horsepower, when push-to-pass and the hybrid ESS boost are both deployed together on a road or street course, on top of a base output above 700 horsepower.
Why does IndyCar need two engine suppliers instead of one?
It's a deliberate design choice within the spec-chassis formula — competition between Honda and Chevrolet on engine performance without opening up full constructor-style chassis development.
What is drafting?
Following closely behind another car to reduce aerodynamic drag and gain a speed advantage — a central technique in oval racing, especially on superspeedways.
Sources
Pippa has followed open-wheel racing for 12 years, from Formula 1's turbo-hybrid era to IndyCar's short ovals, and has watched competitive sim racing grow from a niche hobby into a genuine motorsport discipline in its own right. She covers circuit and open-wheel racing, touring cars and esports for CNMOTOS.
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