Mid-block traffic management: what’s behind those seemingly pointless stop lights in Denver?

I’m rarely one to begrudge municipalities that find creative, site-specific means of managing traffic flow.  If these solutions meet the desired outcome of improving the Level of Service (LOS) at a certain road segment, intersection, or even a single lane of traffic (left-turn, right-turn, or through), and they achieve this without compromising safety for alternative modes of transportation (pedestrians, bicycles, etc.), then why not?  About the only widespread disadvantage I can think of—a disadvantage that standard traffic impact analyses using the latest edition of the Highway Capacity Manual or the Intersection Capacity Utilization method might not capture—is if the solution is so unorthodox that motorists who are unaccustomed to the designed/installed solution either panic or misinterpret it, resulting in a negative overall safety outcome.  But such a result should manifest itself through increased vehicular accidents, or even a lowered LOE.  And, when all’s said and done, if the designed/installed improvements significantly outlay any disadvantages, then the intervention is a de facto net positive.

That opening paragraph offered far too many glittering generalities and too much technical jargon.  Time to bring it down to earth with some examples.  I first witnessed a city-specific example of a traffic management strategy while growing up in Indianapolis.  Commuting northward to downtown from the city’s south side and its suburbs, one encounters a mile-long stretch of South Meridian Street (the city’s prime north-south arterial) where, in an older neighborhood close to the city center, the traffic spreads across three lanes: one northbound, one southbound, and a central lane that in many contexts accommodates left turns only (the notorious “suicide lane”), but on this stretch of South Meridian, it alternates between northbound and southbound traffic depending on the time of day and rush hour.  It’s hardly a cutting-edge solution, but the placement of signage across each lane to guide the flow is a condition I have never seen anywhere else.  Here’s a Google Street View to show what it looks like; notice the red and green signs suspended on wires above the three lanes.  This approach helped preclude a potential road widening that would add lanes in an inner-city neighborhood where the homes have small setbacks from the street.  I’m not sure it’s a brilliant solution, but it’s been this way since I was a child, so if it were catastrophic, the city’s Public Works Department almost certainly would have eliminated it by now.  Elsewhere in Indianapolis, one finds a more complex variant at East Fall Creek Parkway North Drive, a busier corridor accommodating rush hour traffic to the northeast suburbs across five lanes, using overhead colored lights to indicate the flow of that middle lane.

Other localities have devised more engineering-heavy solutions.  New Jersey has long established a reputation for installing impassable three-foot concrete walls along its medians to busy urban arterials; they’ve become so famous they earned the name Jersey barriers.   These impediments essentially preclude left turns, a major contributor for traffic back-ups as vehicles idle at arterial intersections waiting for enough clearance to turn left two to four lanes of traffic.  The widespread presences of Jersey barriers have resulted in another New Jersey phenomenon called the jug handle: an exit spur branching from the right-most lane on an arterial, shaped like its name (or, perhaps easier to conceptualize, half of a Valentine heart), and this spur then straightens to intersect the arterial as a stop light that then allows left turn.  The Jersey barrier and jug handle have imitators elsewhere, but they are ubiquitous in the Garden State.

Meanwhile, Michigan developed its own method for keeping left-hand turns from obstructing lanes in busy arterials, through the Michigan left, a careful deployment of medians and generous shoulders that, again, allows a motorist to make the easier right-hand turn before approaching a busy intersection with the ultimate intent of making a hard left.  Lastly, Washington DC provides complete contraflow on its busy Rock Creek Parkway during the evening rush hour, meaning a typically two-way parkway becomes exclusively northbound for two hours every afternoon, allowing vehicles to leave the Federal Triangle and downtown neighborhoods to make their way to the more suburban quarters of northwest DC and Montgomery County, Maryland with as free flow as possible.  Motorists seeking to head south at this point in time must find some other route.

Every one of the examples I have listed have expanded beyond the original jurisdiction from which they became known.  The one featured in the upcoming photos might be a different story.  At this point, I have never seen anything like the mid-block example below, except in Denver.

From this direction, it’s subtle, but suspended across the street is a stop light, facing ongoing traffic on a one-way street—East 14th Avenue in this case, in an old established neighborhood about a mile and a half east of downtown.  Here’s a view pointing eastward—the same direction as the vehicles:

But there’s something distinctive about the placement of this stop light: it doesn’t seem to service an intersecting street.  Perhaps it’s a pedestrian-only crossing; there does seem to be a clear crosswalk and signal for pedestrians.

But there’s no evidence that this is a particular high-demand site for pedestrian crossing; it’s not like the crosswalk links to a pedestrian-only path.  As the photo below demonstrates, it only links with an alley.

But is the stop light serving the alley itself, giving clearance for vehicles entering onto East 14th Avenue?

That doesn’t appear to be the case; why would it?  Is there ever enough traffic exiting the alley onto a major street to justify a fully signalized intersection?  Not likely.  Seeing the stop lights from a different angle proves that they have nothing to do with the cross street.

In other words, when the light turns red for motorists on East 14th Avenue (as in the photo above), they just idle there, waiting for the rare event when a pedestrian might need to cross.  But that’s not likely to happen very often.  It’s a mid-block stop light, poised between East 14th Avenue’s intersection with Detroit Street and Fillmore Street, two primarily residential north-south streets, which, like the alley between them, do not host enough vehicular traffic to warrant a signalized intersection.  So what’s the explanation for the light?  What exactly does it achieve?

I think it has more to do with long-term configurations to the road itself than any hazards or congestion at this specific location.  It doesn’t take a brain surgeon to deduce that the Denver Department of Public Works has harnessed East 14th Avenue and East 13th Avenue (just one block to the south) as “paired streets” for traffic management; that is, East 14th in the photos is one-way eastbound (away from downtown), while East 13th is one-way westbound (toward downtown).  This approach encourages free flow of rush hour traffic across all three lanes, while spreading the pain more evenly across the two paired streets: East 13th and the surrounding neighbors experiences the congestion in the mornings, when cars from suburbs like Aurora are head to work, while East 14th gets the congestion in the evenings.  Though I strongly suspect both of these roads were two-way at their initial conception well over a century ago, they evolved as complementary one-way streets at some later point in time.  Perhaps each road serviced a trolley or streetcar back in the early 20th century, with 13th being the inbound route and 14th outbound.  (This is mere speculation on my part, and I’m not very confident of it; although 13th Avenue hosts the corner commercial nodes typical of streetcar stops, 14th Avenue is exclusively residential, suggesting that 14th was never a streetcar route.)

Regardless of the history, the heavy flow of traffic during normal rush hour (in normal employment conditions) creates challenges for cars seeking to enter these one-way collector roads from the minor, local streets that intersect them—in this case, Detroit and Fillmore streets.  During rush hour’s peak, the flow of traffic on 13th and 14th avenues is so thick that it’s difficult for vehicles on the intersecting north-south streets to even get their nose in.  It doesn’t help that the major north-south streets are few and far between.  Take a look at this map below:

On the far left (west) is Josephine Street, a busy enough collector road (and one-way north) to justify a light.  On the far right (east) is Garfield Street, a local road, not very busy, but apparently enough traffic again to justify a light.  In between is well over a half-mile of East 14th Avenue amidst a dense, mostly residential area with no real east-west street, and, within these mid-block configurations, no real stop lights.  It may actually prove more effective to have mid-block lights rather than lights at intersections (such as Detroit or Fillmore) because their timing is directly calibrated to high intensity traffic—that is, they remain green during the non-rush hour periods, unless a pedestrian activates them—and there is no north-south traffic entering an intersection when the lights force vehicles on East 14th to stop.  (There’s a mother mid-block light on 14th between Adams and Cook streets, except it doesn’t even seem to have a pedestrian crosswalk.  And many many more mid-block lights on East 13th Avenue.)  As indicated earlier, when these mid-block lights are red, nothing is green, and it gives all vehicles on intersecting streets east of this light a chance to either turn on to East 14th or to pass through.

The idea of passing through reveals one another characteristic to the road configuration that confers benefit to these mid-block lights.  As is often the case in older urban neighborhoods, the street grid doesn’t always yield perfect four-way intersections.  The map above shows how the intersection of 14th and Detroit (or 14th and Fillmore, or 14th and Milwaukee) don’t intersect perfectly.  Detroit Street has a “jog” or imperfect intersection that essentially creates two t-shaped intersections in rapid succession.  Here’s what it looks like on the ground.

Note how the street intersect on the left doesn’t align with the street intersecting on the right (in the background, with all the trash bins). Both are Detroit Street. Lack of regulatory control in the late 19th and early 20th century allowed residential developers to build grids like these, which no doubt fostered quieter residential streets because they precluded early locomotives from zipping through intersections.  (They might also be a simple result of careless platting and surveying.)  Regardless, these irregular intersections pose a safety issue by modern standards, since they force motorists to be hyper aware of intersections positioned dangerously close to one another.  And not all motorists can process the information that quickly.  Subdivision regulations today in most cities prohibit intersections from using the design seen at 14th and Detroit, but many still survive from 125 years ago.  The mid-block stop lights along 14th and 13th (and many others scattered throughout Denver) mitigate the safety concerns posed by these irregular intersections.

Apparently these mid-block stop lights are a minor joke among newcomers to Denver—a head scratcher that’s almost a part of local folk culture.   But they exist to address a precise problem, and, from what I can tell without conducting a traffic impact analysis of my own (something I’m not really qualified to do anyway), they meet the desired goal without deteriorating the LOS upstream.  That is, the lights can remain red long enough to provide relief without exacerbated congestion elsewhere.  People who are initially annoyed at stopping mid-block for no apparent reason eventually see their usefulness. The conditions prompting these mid-block lights do not seem unique to Denver—and perhaps they aren’t—but I’ve never seen them anywhere else, and this solution is hardly as well-known as the New Jersey jug handle or the Michigan left.  Maybe it just takes time.  Traffic in the months ahead could get worse if prolonged COVID-19 considerations scare people away from mass transit, or they could get better if those same precautions encourage millions of commuters to work from home.  None of us have a crystal ball—not even the all-knowing government overlords.  A good reason we should always moderate our criticism of seemingly asinine road design situations.  Much like the irregular intersection at 14th and Detroit, it seemed like a good idea at the time.