Bike advocates frequently repeat a claim that 40% of all trips are two miles or less.

Where does that 40% figure come from. A “Nationwide Personal Transportation Survey” is often cited, but it’s one of those statistics that’s endlessly repeated a bit like that bogus 85% figure frequently mentioned for bicycle helmets. Lisa Halverstadt of Voice of San Diego — a nonprofit investigative news organization — looked into the stats after San Diego’s city council president Todd Gloria repeated the 40% figure during a bike event.

Her shocking discovery — it’s true! Well, sort of. 40% of all trips reported by this national survey in 2009 showed 40% of all trips — whether by car, bus, walking or biking — are indeed two miles or less.

But then Halverstadt dinged Gloria’s statement as “misleading” because when you narrow the mode down to cars only, 69% of trips are two miles or less.

In other words, the ratio of short trips actually goes up, according to Halverstadt. Watch her video report for Voice of San Diego below, or read the text from the Voice website, where you can also see numbers for San Diego residents (37% of all trips, 32% of car trips). And if you know how to tease the data from the database, you can grab it straight from the horse’s mouth at the National Household Travel Survey.