Stopping Distance

{
  "asOf": "2026-10-11T14:38:38.172Z",
  "brakingDistanceFt": 171.9,
  "brakingDistanceM": 52.4,
  "decelerationG": 0.7,
  "degraded": false,
  "disclaimer": "Screening signal computed from the named public source. Not financial, legal or investment advice; provided as is. Verify at the source before acting.",
  "frictionCoefficient": 0.7,
  "gradePercent": 0,
  "notChecked": [
    "tire condition, ABS behaviour, brake fade, vehicle load and tyre pressure, which change friction a lot",
    "that real friction varies: wet or icy roads can be far worse than the table values",
    "…2 more"
  ],
  "reactionDistanceFt": 132,
  "reactionDistanceM": 40.23,
  "reasons": [
    "Reaction distance = speed x reaction time; braking distance = v^2 / (2 g (friction + grade)).",
    "Doubling the speed quadruples the braking distance."
  ],
  "source": "computed locally",
  "speedKmh": 96.56,
  "speedMph": 60,
  "speedMs": 26.822,
  "stoppingTimeSeconds": 5.41,
  "summary": "At 60 mph on dry-asphalt: 40.2 m reaction + 52.4 m braking = 92.6 m (303.9 ft) to stop, taking 5.4 s.",
  "surface": "dry-asphalt",
  "totalStoppingDistanceFt": 303.9,
  "totalStoppingDistanceM": 92.64,
  "verdict": "COMPUTED"
}

# bash or zsh: see the payment challenge. Nothing is charged.
curl -sS -g -i 'https://automotive-calc.x402tookit.com/stopping-distance?reactionSeconds=1.5&speed=60&surface=dry-asphalt&unit=mph'

# x402 v2 sends the challenge base64-encoded in the PAYMENT-REQUIRED header (v1 sends it in the body).
# To read the header:
curl -sS -g -o /dev/null -D - 'https://automotive-calc.x402tookit.com/stopping-distance?reactionSeconds=1.5&speed=60&surface=dry-asphalt&unit=mph' \
  | grep -i '^payment-required:' | cut -d' ' -f2 | tr -d '\r' | base64 --decode

// npm i @x402/fetch @x402/evm viem
import { wrapFetchWithPayment, x402Client } from "@x402/fetch";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

// Pays at most $0.02 per call.
const client = new x402Client().setSpendControls({ maxAmountPerPayment: "$0.02" });
registerExactEvmScheme(client, { signer: privateKeyToAccount(process.env.EVM_PRIVATE_KEY) });
const pay = wrapFetchWithPayment(fetch, client);

// Not sure it's safe to pay? ToolVet checks it first for $0.005. Pay for that from a separate
// client: this one is capped at $0.02 per payment. GET https://toolvet.app/api/v1/check?url=https%3A%2F%2Fautomotive-calc.x402tookit.com%2Fstopping-distance
const res = await pay("https://automotive-calc.x402tookit.com/stopping-distance?reactionSeconds=1.5&speed=60&surface=dry-asphalt&unit=mph");
console.log(res.status, await res.text());

# pip install "x402[requests,evm]"
import os
from eth_account import Account
from x402 import x402ClientSync
from x402.http.clients import x402_requests
from x402.mechanisms.evm import EthAccountSigner
from x402.mechanisms.evm.exact.register import register_exact_evm_client

# Pays at most $0.02 per call.
client = x402ClientSync().set_spend_controls({"max_amount_per_payment": "$0.02"})
register_exact_evm_client(client, EthAccountSigner(Account.from_key(os.environ["EVM_PRIVATE_KEY"])))

with x402_requests(client) as session:
    res = session.get("https://automotive-calc.x402tookit.com/stopping-distance?reactionSeconds=1.5&speed=60&surface=dry-asphalt&unit=mph")
    print(res.status_code, res.text)