#6 Signals Unwinde Slower
#7 It's the Joints Not the Pipe
US 41@Stickney Point 6 lanes+2left+1right
Simple Truths #6 & #7
Simple Truth #6: Signals Unwind Jams Slower.
Intersection flow sometimes is blocked by backup originating elsewhere, like the Venice Ave ICW bridge. Can a modern roundabout unwind a backup quicker than a signalized intersection?
This question deserved research, as Venice raised concern regarding its Venice Avedrawbridge that, when raised, could backup traffic and block US41@Venice Ave That issue was bought to transportation engineers at the recent FHWA sponsored International Roundabout Conference in Carmel, IN, as well as Institute of Transportation Engineers.
Turns out modern roundabouts are today unwinding backup quicker than the signals they replaced (unimpeded by signals cycling red). Here’s “real life” examples:Border Crossings: at the Canadian border - Blaine, WA, & Calais, ME (roundabouts recently constructed by US Customs, not yet on Google maps).
RR Xings: Jensen Beach, FL http://tinyurl.com/42e6bmj (rails thru the middle of the roundabout). Blaine, WA.
Event Release:Virginia Tech Football, Blacksburg, VA http://tinyurl.com/3mmg4rg (delay after games decreased to less than a minute). Since 2000, Clearwater Beach roundabout Spring Break (southwest parking area and garage) http://tinyurl.com/4ymtldk. US41/Gulfstream planned roundabout purpose includes relief of backup onto the Ringling Bridge (pic attached) from St.Armands in-season weekends.
Drawbridge: Astoria, OR,http://tinyurl.com/4yvsszx & Daytona, FL, (with volume similar to US41Venice Ave) until drawbridge was replaced by fixed span bridge.
Related:
Crashes: A head-on or broadside crash at signalized intersections blocks flow until cleared. Roundabout accidents are fender benders that can usually move themselves on through the roundabout & exit to the road side, momentarily slowing traffic.
Hurricane Evacuation: Unlike a signalized intersection, a roundabout is not disabled by electric power outages or signal cross arms blown down into the intersection.
Simple Truth #7: It’s the joints, not the pipe.
Along US41 through Manatee & Sarasota counties Intersections Determine Traffic Flow!…It'sall about managing the intersections.
Plumber lingo: it’s the joints, not the pipe! Traffic Engineer* lingo: narrow roads, wide nodes!
See: *Federal Highway Administration (FHWA) www.fhwa.dot.gov ,
Transportation Research Bureau (TRB) http://trb.org/,
Institute of Transportation Engineers (ITE) www.ite.org.
What better cost/benefit best practice can deliver Venice the congestion relief sought and deserved by its residents and businesses in a way that promotes livability in the broad Venice community?
Part One: *FHWA & TRB December 2010 Roundabout Guide, page 39: “Roundabouts can be made as large as needed for node [intersection] capacity*, keeping the links between nodes more narrow. This concept is referred to as a “wide nodes, narrow roads.” and is illustrated in Exhibit 2-1.” See Page 40 (exhibit 2-1)) @ http://tinyurl.com/3z6eej4,
Part Two: FHWA & TRB 2010 Roundabout Guide, page 80 …” Roundabouts offer the potential for reducing special requirements on approaches compared to conventional intersections. This effect of providing capacity**at the intersections while reducing lane requirements between intersections is known as the wide nodes, narrow roads concept.”
Regardless roundabout or signaled ByPass @ at Venice Ave will be a WIDE NODE ... with a difference - the roundabout node will not need long, long “holding lanes” for vehicles waiting/idling for the red light to turn green (see Venice Ave signals design below) – i.e, roundabout nodes do not need “holding lanes.” A “Wide Nodes, Narrow Road” ByPass retaining its four lanes requires less ROW (Right of Way) taken by the state near the Venice Ave node (and at Albee Farm, Bird Bay, etc). A roundabout wide node (moving 30% more capacity** than signaled) would not be as LONG in length as the designed Signalized Wide Node = Nine lanes Wide extending more than three football fields, 330 yards north and south of Venice Ave!
Corollary > A corridor’s highest volume signalized intersection (US41ByPass/Venice Ave) is a “mother hen” that obliges other ByPass signaled intersections to fall in line as her “little ducklings in a row”-- lesser volume STOPlights timed to react to the vehicle platoons released by the mother hen’s red/green signal cycling. The heavy crossing vehicle volume at mother hen US41ByPass/Venice Ave means long reds & greens for through and crossing drivers taking turns using that intersection (but at a roundabout all directions of flow are using the intersection at once – efficient!). The ducklings’ STOPlights timed ready for the mother hen’s released platoons will fail when needed most, click Simple Truth #5: Timed lights fail when needed most -- not at all needed by the ducklings in line when the mother hen is a roundabout …
Simple Truth # 7: It’s the joints, not the pipe.
With a reliable traffic demand forecasts and valid comparison of before and after mobility impact of four lanes vs six lanes - signals or modern roundabouts . . .
1) The MPO cost/benefit mission of safer smoother traffic flow soonest is best met, 2) Venice residents’ deserved congestion relief is best served,3) The multimodal principles of this MPO’s adopted 2035 Long Range Transportation Plan best honored.Key: An MPO selection of a proved better cost/benefit could achieve the relief sought by Venice while freeing up several million dollars for waiting US 41 mobility needs from Palmetto to the Charlotte County line.
