Measured day · heading down
Cape Cod traffic on Friday, August 21
792 readings on the day, compared against 11 other measured Fridays (10,511 readings in all). Every figure below is measured — nothing is modelled or estimated.
How this Friday compares
Each grey line is one measured Friday. Friday, August 21 is drawn over them, so the question isn’t what the delay was but where it sat among the Fridays we’ve actually recorded.
| Hour | Friday, August 21 | Typical Friday | Range across Fridays |
|---|---|---|---|
| 10 AM | 19 min | 17 min | 4–37 min (n=11) |
| 11 AM | 14 min | 22 min | 10–41 min (n=11) |
| 12 PM | 18 min | 24 min | 14–38 min (n=11) |
| 1 PM | 18 min | 29 min | 18–38 min (n=11) |
| 2 PM | 23 min | 31 min | 6–35 min (n=11) |
| 3 PM | 22 min | 24 min | 0–34 min (n=11) |
| 4 PM | 16 min | 15 min | 0–24 min (n=11) |
| 5 PM | 10 min | 8 min | 0–16 min (n=11) |
| 6 PM | 2 min | 2 min | 0–7 min (n=11) |
| 7 PM | 0 min | 0 min | 0–3 min (n=11) |
| 8 PM | 0 min | 1 min | 0–2 min (n=11) |
| 9 PM | 0 min | 0 min | 0–0 min (n=11) |
“Typical” is the median across the other measured Fridays, shown only for hours at least three of them recorded. Not a percentile — with 12 fridays the honest summary is the observed range.
Which routes drove it, at 2 PM
Delay in minutes, and what that is as a share of the route’s clear-road time. The share matters: a long drive collects more absolute minutes without being more congested.
| From | Sagamore Bridge | Bourne Bridge | Hyannis |
|---|---|---|---|
| Boston | 41 min +68% | 39 min +61% | 47 min +59% |
| Providence | 6 min +10% | 5 min +9% | 11 min +13% |
| New York City | 84 min +35% | 86 min +37% | 85 min +33% |
| Hartford | 26 min +20% | 25 min +20% | 27 min +18% |
| Worcester | 13 min +15% | 13 min +16% | 19 min +17% |
| Plymouth | 14 min +50% | 16 min +50% | 20 min +43% |
By share of a clear run, the worst route at 2 PM was Boston → Sagamore Bridge — 41 minutes on a 60-minute drive (+68%). New York City → Bourne Bridge lost more raw minutes (86), but on a 233-minute drive that is a smaller share — which is why ranking by minutes alone mostly ranks routes by length.
Methodology
Drive times are collected every 15 minutes during Cape Cod travel windows via the Google Routes API, measured to the mainland approach of each bridge so the figure isolates the crossing rather than on-Cape traffic. Delay is the with-traffic time minus that route’s free-flow baseline; readings more than 3× free-flow are excluded as routing outliers.
Comparisons use only the 18 routes sampled at every capture. Origins sampled hourly are shown on the day’s own figures but kept out of cross-day comparison, because a route measured four times an hour and one measured once would otherwise appear to differ for reasons that are about sampling rather than traffic. The network median is the median across those routes of each route’s hourly median — taken across routes, not across readings, so a heavily-sampled route can’t pull the number toward itself.
Days are frozen from the raw readings once finished, so these figures stay citable after the raw rows age out of retention. Raw readings (CSV) · CC BY 4.0 — cite “Cape Cod Traffic (cape-cod-traffic.com)”.
Driving down this Friday?
On Friday, August 21 the 10 AM–5 PM window was the one to avoid. Live readings tell you whether this Friday is tracking the same way.