Calmarea traficului

PowerPoint PresentationPricipalele solutii constructive aplicate in practica diferitelor administratii
SOP Chapter 3
Seminar Session 2 reviews the advantages and disadvantages of traffic calming measures and demonstrates several experiences with the application and design of the more common measures.
Solutii constructive pentru calmarea traficului – Confdr.ing.Valentin ANTON
Trasee inchise
(cul-de-sacs, dead ends)
SOP Chapter 3
Full street closures are barriers placed across a street to completely close the street to through-traffic, usually leaving only sidewalks open
Barriers may consist of landscaped islands, walls, gates, side-by-side bollards, or any other obstructions that leave an opening smaller than the width of a passenger car
Reducerea latimii partii carosabile la intersectii
(partial closures, one-way closures, directional closures)
SOP Chapter 3
Half closures are barriers that block travel in one direction for a short distance on otherwise two-way streets
When two half closures are placed across from one another at an intersection, the result is a semi-diverter
Half closures are most common volume control measure after full closures
Amenajari diagonale
SOP Chapter 3
Bariere mediane
SOP Chapter 3
Median barriers are raised islands located along the centerline of a street and continuing through an intersection so as to block through movement at a cross street
Insule pentru canalizarea traficului
SOP Chapter 3
Forced turn islands are raised islands on approaches to an intersection that block certain movements
Denivelari scurte ale suprafetei carosabilului
(bump)
Speed humps are rounded raised areas placed across the road
In a survey by the Urban Transportation Monitor, speed humps were rated both the “best” traffic control technique and the “worst,” depending on who was responding
“Best” because very inexpensive and very effective in reducing operating speeds and cut-through volumes (the latter, where alternate routes exist)
“Worst” due to aesthetics, rough ride, and perceived liability
Note discussion on concerns over potential liability as discussed in
SOP Chapter 4
Denivelari extinse cu pavaje distincte
(trapezoidal humps, flat topped humps)
SOP Chapter 3
Speed tables are flat-topped speed humps often constructed with a brick or other textured materials on the flat section
22’ tables are used in 11 of the 20 featured communities, exclusively in three of them
Longer speed tables are gaining popularity relative to speed humps due to:
Better aesthetics
Gentler rides
Ability to serve as raised crosswalks
Also note the downside of speed tables:
Higher cost than speed humps, anywhere from a few hundred to thousands of dollars per table (depending on materials)
Insufficient speed reduction in certain applications
Amenajarea geometrica a denivelarilor
Source: Bureau of Traffic Management, “Traffic Manual” Portland, OR, December 1994, Chapter 11
Source: Clement, J.P “Speed Humps and The Thousand Oaks Experience.” City of Thousand Oaks.
Thousand Oaks, CA, September 1982
SOP Chapters 3 and 7
Parabolic profile is most common in the U.S.-- it is the profile recommended by ITE
Yet, it is also the profile that is steepest at the point of intersection with the roadway surface
Circular profile developed in England is flatter at the point of intersection and hence gentler
Sinusoidal profile developed in the Netherlands is absolutely flat at the point of intersection and is recommended in the Canadian Guide to Neighbourhood Traffic Calming
Trapezoidal profile (flat-topped) used throughout Europe has two abrupt changes in slope and hence has the lowest design speed for the same length and height
In practice, the exact shape of a rounded hump is difficult to achieve with asphalt. It is important that the specifications provide tight tolerance on the height and shape
Several manufacturers now offer prefabricated humps that should lead to more uniform humps and make street resurfacing easier
Denivelari ale carosabilului la intersectii
(raised junctions, intersection humps, plateaus)
SOP Chapter 3
Raised intersections are flat raised areas covering entire intersections, with ramps on all approaches and often with brick or other textured materials on the flat sections
Characteristics:
Usually rise to sidewalk level, or slightly below to provide a “lip” for the visually impaired
Make entire intersections, crosswalks and all, pedestrian territory
Are relatively costly, which discourages the use of raised intersections
Cost may be minimized by using simple asphalt, as in photo on right, but at the expense of aesthetics
Mini-giratii
Traffic circles are raised islands, placed in intersections, around which traffic circulates
Characteristics:
Block the straightaway, thus slowing traffic at the location of highest collision potential, the intersection
Usually circular in shape, though not always
Usually landscaped in their center islands, though not always
Often with outer rings (called truck aprons) or conical shapes (with “lips”) that are mountable so large vehicles can circumnavigate their small curve radii
Giratii
SOP Chapters 3, 4, and 9
Roundabouts have been used as both traffic calming measures for higher order streets and intersection control devices that substitute for all-way stops or traffic signals
Their traffic calming effect is due to:
Deflection at the entry point
Horizontal curvature of the circulating lane
Relatively low speeds at entry give roundabouts a significant safety advantage over other forms of intersection control, documented in several before-and-after collision studies
Giratii vs. Mini-giratii
Both roundabouts and neighborhood traffic circles require traffic to circulate counterclockwise around a center island
What distinguishes roundabouts from neighborhood traffic circles are:
Use on higher order streets to allocate rights-of-way among competing movements
Higher design speeds appropriate to the higher order streets
Larger center islands, larger outer diameters, and larger curb return radii on the corners
Raised splitter islands to deflect approaching traffic and channel it to the right
Roundabout at upper left from Tallahassee, FL
Neighborhood traffic circle at lower right from Seattle
Trasee sicanate
SOP Chapter 3
Chicanes are curb extensions that alternate from one side of the street to other forming s-shaped curves
Chicanes are not used much in the U.S., at least as yet, due to the relatively high cost of right-of-way, curb realignment, and landscaping
Alte amenajari geometrice in plan
Alinierea intersectiilor
Extinderi laterale
Realigned intersections are changes in alignment that convert T-intersections with straight approaches into curving streets meeting at right angles
Lateral shifts are curb extensions on otherwise straight streets that cause travel lanes to bend one way and then bend back the other way to the original direction of travel
Reducerea latimii partii carosabile la accese in intersectii
(nubs, bulbouts, knuckles, intersection narrowings, corner bulges)
SOP Chapter 3
Neckdowns are curb extensions at intersections that reduce roadway width
If coupled with crosswalks, they are referred to as safe crosses
Their effect on vehicle speeds is limited by the absence of pronounced vertical or horizontal deflection
Instead, their primary purpose is to “pedestrianize” intersections
Reduceri locale ale latimii partii carosabile
(pinch points, midblock narrowings, curb extensions, midblock yield points)
SOP Chapter 3
Chokers are curb extensions at midblock that narrow a street by widening the the sidewalk or planting strip
If marked as crosswalks, they are also called safe crosses
Chokers can leave the street cross section with two lanes, albeit narrower lanes than before, or take it down to one lane
Insule centrale
SOP Chapter 3
Center island narrowings are raised islands located along the centerline of a street that narrow the street at that location
Detalii de amenajare
SOP Chapter 4
Standard Canadian design
Note geometric parameters, signing, and marking
Note that the above image was taken from the Draft Canadian Guide to Neighbourhood Traffic Calming for demonstrative purposes. The published report contains the final version of the standard Canadian design and is available for purchase through the ITE Bookstore at 202-554-8050 ext.130
Amenajari pentru traversari pietonale
Source: City of Toronto, Urban Design Guidebook - Draft for Discussion, Toronto, ON, Canada, 1995, p.25
SOP Chapter 3
Alternative designs for safe crosses, the top two involving neckdowns at intersections, the bottom involving a midblock choker
Taken from City of Toronto, Urban Design Guidebook - Draft for Discussion, Ontario, 1995, p. 25
1.bin
Like other narrowings, center islands can help pedestrianize streets
Center islands provide a refuge for pedestrians crossing half way, waiting for a break in the traffic, and then crossing the other half
Center islands are even more pedestrian-friendly when combined with crosswalks and divided to provide a crossing entirely at street level
SOP Chapter 3
Placed at the entrance to a neighborhood, and often combined with textured pavement, center island narrowings are called gateways
Upper left is at midblock -- Ft. Lauderdale
Lower right is at an intersection -- Bellevue
Masuri combinate pentru siguranta circulatiei
SOP Chapter 3
Trend toward combined measures has already been described (Seminar Session 1)
Examples:
Upper left -- raised crosswalk with choker in West Palm Beach
Upper right -- speed table with center island in Boulder
Lower left -- center island with neckdown in Eugene
Lower right -- center island with chokers in Tallahassee
Costuri estimate pentru sistemele de siguranta a circulatiei
speed humps $ 2 000
speed tables $ 2 500
raised intersections $ 12 500
SOP Chapter 3
Completing the overview of traffic calming measures is this table of “standard” costs
Costs increase quickly when measures require landscaping, drainage improvements, or land acquisition
Standard cost estimates are a conceptual planning tool that cannot replace detailed cost estimates using quantities and unit prices
Companion Canadian

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Calmarea traficului