20 is plenty!! 15 Minute Cities!

 In my neighborhood, there are no posted speed limits for residential streets, except the main mid-mile feeder which got signage because everybody drove far faster (and still do, despite some speed-humps).

That means that the speed limit is the city default of 25mph, unless otherwise marked...every residential street, including cul-de-sacs.  The feeder street is marked 25mph, while the arterials are 40mph (2-lane) or 45mph (5-lane) depending.

A lot of places are talking about the notion of 15-minute cities, where almost all of your daily needs are within a 15 minute walk.  Other places are talking about "20 is plenty"  -- 20mph max speed anywhere in town.    These notions seem to fit together nicely, since more accessibility to daily needs by food or bike means that fewer trips are made by car, and so a few extra minutes of driving now and then isn't really a very big deal.

Today I had a fairly routine trip to the local hardware store.  This is the sort of trip that I might have done by bike if only it were possible.  In theory I COULD have biked there on the 45mph (50+mph actual speed) arterial, but I value my life.  I probably COULD have picked a path through neighborhoods, but even this takes dog-leg runs along the arterials to cross between mis-aligned side streets, and it adds an extra mile or so, and I'd have to navigate the maze with Google Maps.  Plus, the ride is not terribly pleasant as no drivers are watching for cyclists so you have to watch every driveway and minor intersection closely. 

So I drove....5 minutes each way, almost exactly...for 2.5 miles, staying in the slow lane at the speed limit of 45mph on the arterial, and 15mph in the neighborhood. 

What if....

....I had bike lanes along the arterials, and a decently safe intersection crossing?  At 10mph it'd be a 15 minute ride each way...not bad, but not great.

...I had a hardware store with my 15-min neighborhood?    A 15-min half-a-mile walk would only be 5 min or less by bike, so I'd be set.

...I lived in a "20 is plenty" city, with even slower 10mph residential streets?  My house is less than 1/4mi from the arterial...3/4 of all houses are (the rest are close to a feeder).  At 10mph, I'm still under 30s from the arterial stop sign...would have to hustle to hit the 25mph limit actually (and yes, many drivers do!).  In any case, compared to my nominal drive, 10mph residential limits would add only 5 or 10sec to the residential leg.

2.5 miles driving on the arterials took a little less than 5 minutes, include making one light and missing one, so the reasonably range would vary by +/- 30s for lights -- 4.5 to 5.5min.  Driving each mile at 40mph takes 1.33 min, so acceleration, deceleration, left-turn across traffic, etc. take about a minute of the trip, and driving takes 3.33 min, more or less.

At 20mph, each mile takes 3 minutes, or 7.5 total.  That adds a bit over 4 minutes to the drive....less than double overall.


But here's the kicker:  my drive today was Sunday afternoon, with very little traffic.  During heavy traffic times, the lights get backed-up, and lane changes and turns further slow the roll.  The sprints to 50mph in the mile-long open stretches feel like progress, but they don't save very much time -- generally less savings on longer overall drives -- especially during rush hour.  Already most of the rush-hour delay is at the intersection, so why not neck-down the mile in-between to 2 lanes, or maybe 3 in some sections, but add a mid-mile crossing for bikes and peds?

By happenstance, this 2.5 mile distance is about the average distance from a residence to the ring highways...a bit more or less, depending on where you're trying to go.  Maybe if 10min per day added drive-time is too long to justify a quiet, safe, neighborhood, an individual should re-evaluate their life and either simplify their travel needs or move closer to their all-important destinations. 

I'd be willing to make the trade.




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