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Source: xkcd #3167 – "Car Size" — Licensed under CC BY-NC 2.5.

When the Interface No Longer Fits the Street

"Car Size" looks like a joke about trucks wedged into narrow lanes. It’s not. It’s about us. In the comic, the physical world—roads, parking spaces, city geometry—stays constant while vehicles swell absurdly out of proportion. What used to fit elegantly now scrapes, blocks, and breaks its environment. For anyone building software in 2025, the metaphor is uncomfortably familiar: product surfaces stay the same size (the viewport, the mental model, the use case), while the features, frameworks, tracking pixels, and visual noise keep getting bigger. The result is predictable: friction, failure, and a quiet normalization of collateral damage.

Feature Creep as Vehicular Obesity

We’ve trained ourselves to accept that every release must be justified by visible change:

  • Another banner.
  • Another modal.
  • Another SDK.
  • Another permissions scope.
  • Another megabyte of JavaScript.

Individually, each is defensible. Collectively, they’re an F-150 in a world built for a Civic. Developers know the pattern:

  • UI Sprawl: A settings page that now requires three levels of navigation, a search bar, and a doc to explain.
  • API Bloat: Endpoints that return 60 fields where six are used, maintained forever because of one integration written five years ago.
  • Client Weight Gain: A landing page that ships a single paragraph of text atop a 4 MB JS bundle and five analytics tags.

The street (your user’s context, time, bandwidth, and cognitive capacity) has not changed. Your car has.

The Hidden Costs: Latency, Complexity, and Cognitive Debt

Oversized software doesn’t just feel clumsy; it encodes structural risk.

  1. Performance Degradation

    Heavy clients and sprawling backends mean worse cold starts, poorer mobile performance, and more infra spend. For many teams, “we’ll optimize later” has silently become “we’ll bill the user and the planet instead.”

  2. Attack Surface Expansion

    Every extra integration, permission, cookie, and plugin is more metal sticking out into live traffic. Oversized applications increase:

    • exposed endpoints
    • complex auth paths
    • third-party scripts with unclear patch/ownership chains
      This is how "just one more" integration becomes the pivot point for real security incidents.

  3. Operational Drag
    Larger systems are harder to reason about. On-call rotations suffer because even senior engineers can’t hold the whole topology in their heads. TTR (time to repair) stretches, and incident retros start to sound like traffic reports.

  4. User Hostility (Disguised as Growth)
    Growth experiments layered endlessly on top of each other become the SUV grille pressed against the crosswalk. Newsletter overlays, upsell nags, tracking prompts, cookie walls—all fighting to occupy the same fixed viewport.

Standards Creep and the Normalization of Overkill

The comic also riffs on standards and regulation—how rules shaped for one era quietly break when the underlying objects grow. The parallel in tech:
  • Bundles that were acceptable at 200 KB are rubber-stamped at 4 MB because "that’s just the modern web."
  • Permissions that were once exceptional (location, contacts, clipboard, full-drive access) become boilerplate.
  • Infrastructure defaults sized for yesterday’s monolith get applied uncritically to dozens of microservices.

All of this is technically within spec, just as oversized cars are technically within legal limits, right up until a curb, a cyclist, or a narrow street turns compliance into collision.

Building Software That Actually Fits

If "Car Size" is a warning, what does a right-sized response look like for teams shipping code today?

1. Design to the Street, Not the Showroom

Start with constraints:

  • Assume low bandwidth, high latency, limited attention.
  • Treat the user’s mental model as a scarce resource.
  • Design so that new features displace or simplify, not just accumulate.

In practice:

  • Enforce performance budgets at build time.
  • Require justification for every new dependency or script.
  • Gate UX experiments behind hard caps on layout shift, cumulative UI noise, and JS weight.

2. Make Complexity a Billable Line Item

Complexity will happen; pretending otherwise is denial. Make it explicit:

  • Track dependency counts, owned services, public endpoints, third-party scripts as first-class metrics.
  • Treat each as carrying carrying costs: maintenance, security review, observability, incident response.

This turns "let’s just add X" into "are we willing to support X at 02:00 during an outage for the next 3 years?"

3. Shrink the Attack Surface on Purpose

Security teams have long understood what "Car Size" jokes about:

  • Excessive capability == excessive liability.

For dev and product teams, that means:

  • Minimize scopes and tokens.
  • Avoid unvetted third-party components for trivial problems.
  • Remove dead endpoints, unused flags, and zombie admin panels.

Deliberate deletion is one of the strongest security controls you have.

4. Institutionalize Deletion as a Feature

Roads work when vehicles are designed to fit; software works when teams are allowed to remove things.

  • Allocate roadmap time explicitly for subtraction.
  • Celebrate feature removal in changelogs and release notes.
  • Run regular complexity reviews: what can we unship without harming core value?

Healthy platforms evolve like well-planned cities, not like parking lots stuffed with whatever fits today.

When the Joke Stops Being Funny

"Car Size" lands because we’ve all seen the oversize truck that makes a previously functional space suddenly unusable. The same quiet shift is happening in our stacks, our UIs, and our standards: products that once fit their environment now dominate it.

For developers, engineering leaders, and security teams, the comic is a clean architectural test: Does what we’re building still fit the street it drives on? If the honest answer is no, the fix isn’t a wider road. It’s a smaller, sharper, more intentional machine.