How accurate are our forecasts?

Over the last 13 days (28 October to 9 November 2026), the lane had switched by our “expected by” time on 309 of 325 cards checked: 95%. Over the twelve weeks before (3 August to 27 October 2026), with each week forecast only from earlier days, it was 92% of 9,243 checks. Our aim is nine in ten. Before 10 am we fall short (88% in both), so the home card marks a morning forecast “low confidence”.

No. It publishes approximate weekday times: two lanes southbound from 6:00 to 9:30 am, and mostly two lanes northbound from 3:00 to 7:00 pm. Operators switch the lane by hand, around the clock, “based on traffic, visibility and weather conditions” (Government of British Columbia). On 55 weekdays from 10 August to 9 November 2026, the lane changed direction a median of 27 times a day, and from 3:00 to 7:00 pm it was northbound 65.5% of the time. Is our forecast better than the published times? Not for the first switch of the morning: on those weekdays, 9:30 am and our usual time for that weekday both missed by a median of about 13 minutes. What the published times do not give is the time of the next switch. For the lane right now and for closures, see DriveBC.

No. The Lions Gate Bridge Museum is independent of the province and of DriveBC. Our forecasts are estimates. For closures and road conditions, DriveBC is the official source.

A little, and mostly in the first three months. We built the forecast from one, two, three, five and seven to eight months of earlier data and tested each on the same days it had never seen. With one month, its best single guess of the switch time missed by about two minutes more than with five to eight months (on 28 October to 9 November 2026, 10.5 against 8.7 minutes). After three months, more data changed little. The “expected by” time held about as often either way. The record we learn from started in February 2026, so eight months is all there is.

On weekdays, at about 6 am, southbound first: it opened between 5:50 and 6:10 am on 141 of 151 weekday mornings from 18 February to 8 November 2026. Weekends are later and less regular: on Saturdays the median was 8:08 am and on Sundays 8:20 am, mostly northbound first. How close our opening time came, from 1 April to 9 November 2026: on 124 weekday mornings, a median miss of 2.1 minutes; on Saturdays 20 minutes (27 mornings) and on Sundays 21.6 (26 mornings).

Usually between 9:35 and 9:45 am: that was the median first switch on each weekday from 19 February to 6 November 2026 (Sunday: 9:55 am). Since late October it has often come after 10 am. When the home card says “usually”, it describes past days. It is not a forecast.

Usually a few minutes. Most daytime closures are a switch: the lane closes, then opens the other way. Of 4,499 switches from 19 February to 7 November 2026, half took 3 minutes or less and 99% took less than 10. A closure for an incident or for maintenance is longer: of 42 such closures, half took 30 minutes or more.

They are the museum’s five levels for the extra minutes a trip takes over a clear run. Southbound: Clear under 3, Slow 3 to 8, Congested 8 to 15, Heavy 15 to 25, Severe 25 or more. Northbound, on the bridge deck only: under 1, 1 to 2, 2 to 4, 4 to 8, 8 or more. From 18 February to 28 October 2026, a weekday afternoon (3 to 6 pm) southbound was Heavy 43% of the time.

Two ways. We run the live forecasting code again on past days, using only what was known at each moment, on days its model had never seen (28 October to 9 November 2026). And for the twelve weeks before, each week was forecast by a version built only from the days before that week. Each forecast is then compared with the lane record of that day. This is not a log of what the site showed: no such log is kept yet. The delay forecast is compared with the sign’s own reading an hour later, and with our own estimate of the delay; neither is an independent measurement.

Yes, under CC BY 4.0. Download the weekly summary below. It holds summary figures only, not detector readings. Please credit Lions Gate Bridge Museum (lionsgatebridge.org).