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Traffic signs, while often considered peripheral design elements, play a critical role in communicating a variety of information to users of the transportation system. Signs are used to guide, warn, regulate, and convey information to vehicular and pedestrian traffic along the roadway.

The Manual on Uniform Traffic Control Device (MUTCD) provides guidance on the design and placement of signs, including the size of the sign and text, placement along the roadway, and standard information to be conveyed. Most states, including Missouri, use the MUTCD as the primary guide for developing roadway signage. Some states, such as Illinois, provide supplemental guidance that builds upon the information in the MUTCD. Engineers and contractors also use standard drawings, similar to those provided by the Missouri DOT, to ensure that signs are designed and constructed appropriately.

Traffic signs are often one of many traffic control devices that users must process while navigating streets. Therefore, it is important to design and position signs in a manner that ensures that users have enough information to safely and efficiently navigate the street network without becoming distracted or overwhelmed.

Credit: CH2M HILL

The MUTCD specifications help ensure a minimum level of uniformity among traffic signs nationwide. Uniformity is a critical component of effective traffic sign communication, as users are better able to recognize and respond to familiar signs. Although some jurisdictions may wish to modify the standard sign types to be more attractive, the majority of traffic signs are required to conform to the MUTCD specifications. One exception is street name signs, which may be customized and used to help create a theme or identity for a place. Many agencies are developing artistic street signs, such as the Washington Avenue sign in downtown St. Louis shown at right, to add character to the streetscape.

The ITE Traffic Handbook indicates that traffic control devices, including traffic signs, should:

• Meet a need
• Command attention
• Convey a clear and simple meaning
• Command respect of the road users
• Give adequate time for proper response/reaction

Characteristics that influence signing for residential thoroughfares:

• Significant pedestrian presence
• Slower speeds
• Numerous parking regulations

Pedestrian presence requires effective communication to vehicular traffic.  For residential streets to be great, pedestrians must feel safe from and respected by the adjacent vehicular traffic.  Traffic signs are one way to nurture this relationship.  Appropriate signage in advance of intersections and mid-block crosswalks are important to alert drivers of potential pedestrian crossing locations.  These signs might be installed with flashing lights to better command driver attention.  Enforcement is also important to make sure that the signs are abided by.  Enforcement of pedestrians to limit jay-walking and other improper street crossing is equally important.

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Mid-block crossings are important elements along residential thoroughfares. The picture at right depicts a great example of actuated mid-block pedestrian crossing signs. When a pedestrian presses the button below the sign, the lights on the sign begin to flash, signaling the oncoming traffic to stop. This treatment goes beyond our typical signage to place greater emphasis on the pedestrian.  In addition to the sign, special pavement markings are placed in advance of the crosswalk to represent the "yield line" at which vehicles are to stop when the signs begin to flash. 

This additional provision provides a buffer zone between the crosswalk and the vehicular traffic, aiding the pedestrian's effort to visually confirm that oncoming traffic has come to a stop. Just as traffic signs are important to control and direct vehicular traffic, pedestrian-scale signing is equally important along small town downtown streets.

Signing should also be used to clearly communicate the presence of multi-modal uses and services along the street.  If bicycles are common along the corridor, appropriate “Share the Road” signs should be strategically placed along the street as a reminder to drivers. 

But again, we must go beyond the mere accommodation of other modes such as bicycles; we must prioritize them.  Signing is just one of many ways to accomplish such a prioritization.  The photo at right demonstrates a simple sign treatment at an intersection.  The sign prohibits right turns to vehicular traffic, but "excepts" bicycles.  It's a simple but effective way to prioritize bicyclists and raise driver awareness to bicycle presence along the street. 

Way-finding signs help to effectively guide and inform the numerous pedestrians along the street. These pedestrian-scale signs place a priority on pedestrian travel along the thoroughfare, and they can also visually enhance the streetscape. Way-finding signs can be particularly useful in directing (and encouraging) pedestrians to transit connections nearby. They provide a subtle reminder to residents that there are other mode choices available to them.

Residential neighborhoods will often have children playing in the yards and other open areas abutting the street.  There are signs that can be posted to warn drivers of such presence, thus making drivers better prepared to stop in the event of a child that may inadvertently stray into the travel way of the road.  In addition to children at play, bicyclists and dog-walking pedestrians are also common within residential place types.  Appropriate signage can make drivers more aware of the active pedestrian environment through which they are driving.

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Slower speeds in residential place types make it easier for drivers to process information provided by traffic signs.  One of the challenges, though, is keeping the speeds low.  It is not uncommon for through-traffic on residential streets (especially those that are part of the arterial network) to drive above the speed limit in an effort to minimize travel time.  Speed limit signs should be diplayed intermittently along the street to remind drivers of the lower speed limit.  Speed limit signs alone, though, are not sufficient enough to maintain the desired low speed of travel.  Enforcement is an effective measure, but it is costly to have continuous enforcement.  Studies have shown that when enforcement measures are removed, vehicles typically resume their higher speed of travel.  One measure that has proven to be effective in Minnesota is to use speed limit signs in conjunction with radar speed measurement displays <see PDF>.  While not appropriate in all locations, they have proven to be particularly beneficial in areas that are plagued by travel speeds exceeding the speed limit.

Trees, bushes, and other large landscaping features are not uncommon along residential streets.  Effective sign placement should consider how such features might obstruct the sign from driver view.  Homeowners and street maintenance departments should be vigilant about maintaining the reach of tree branches and bushes to insure that they do not interfere with traffic sign visibility.  A "Children Playing" sign will do no good if it is hidden from view by a maturing tree branch. Consider how new vegetation might impact signing once the vegetation is fully matured, not just when it is initially planted.

The types of drivers expected to be present in residential neighborhoods should be considered when planning and designing signing along the street.  With ever-increasing life expectancies, drivers are older than they once were.  Recent research suggests such drivers have difficulty reading smaller signs. Special consideration of sign size and text/font size for signs should reflect this, especially in neighborhoods of high elderly population.

Article

When rain falls in natural, undeveloped areas, storm water is able to permeate the soil and return to the water table below the surface.  Developed areas have a greater concentration of impervious surfaces such as roads, sidewalks, buildings, and parking lots, which slow or prevent water from permeating the soil.

Natural conditions limit runoff

Development increases runoff

In developed urban and suburban areas, enclosed drainage systems are often used to collect and transport storm water during and after rain events.  When rain falls onto an impervious surface such as a paved road, the water follows the slope of the pavement to a gutter.  The gutter directs the water along the curb line to a series of intermittent inlets where it can enter the collection system below the pavement.  A system of pipes below the pavement moves the collected stormwater offsite to creeks, streams, or other bodies of water in the surrounding hydrologic environment. 

How can we make this...

function more like this?

Low Impact Development (LID) is an alternative method of stormwater management which is used to decrease runoff in developed areas by increasing surface permeability and seeking opportunities to store or utilize stormwater on site, as shown in the images below (e.g. underground storage, rain gardens, downspouts that empty into landscaping rather than the street). 

CH2M HILL

CH2M HILL

Drainage systems for arterial streets will in most cases require a combination of conventional and LID stormwater management methods.  Combining these methods can be especially effective in retrofit situations where existing enclosed stormsewer systems are unable to handle the additional runoff created by new development.  In this situation, using the LID method can be much more cost-effective than rebuilding the storm sewer system.

CH2M HILL

Effective stormwater management is imperative, regardless of which method or combination of methods is utilized.  Flooding of roadways, bike paths, sidewalks, and adjacent properties can create safety and access issues and significant property damage.

Considerations for stormwater management strategy selection:

• Enclosed drainage systems are typically costly to construct and/or rebuild.
• Enclosed drainage systems tend to have significant maintenance requirements.  Without routine maintenance, debris can build up in inlets, curb and gutter systems, and pipes, limiting the system’s effectiveness.
• Enclosed drainage pipes increase the velocity at which stormwater travels, which can exacerbate the erosion of stream banks and channels.  Installing erosion control devices and/or energy dissipaters creates an additional cost.
• The design process for an enclosed drainage system is generally more straight-forward than utilizing LID strategies.  While there is an established set of guidelines and software to direct the design and sizing of enclosed system pipes and inlets, additional research on LID controls and the development of models to validate proposed solutions is needed.
• Reviewers and regulators may be hesitant to approve non-standard drainage system approaches due to the lack of existing design standards and procedures.  Further development of regional guidance to assist reviewers and regulators and pointing to local models of successful implementation could help reduce uncertainty.
• LID strategies can result in some puddling which, although innocuous, some may find aesthetically objectionable or bothersome.  However, many LID strategies (e.g. landscaping, green roofs, and rain gardens) offer significant aesthetic benefits.
• Shared use of parking (e.g. daytime use for offices, nighttime use for a movie theater or restaurants) is a strategy which can be used to reduce the amount of space needed for parking, decrease impervious surface area, and presumably reduce stormwater management requirements.
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  Credit: East-West Gateway
  Pervious pavement can also be used in parking lots to further reduce the impervious surface area.  Pervious pavement is more permeable than regular pavement and allows stormwater to more easily drain through to the soil.  See the EPA Porous Pavement Fact Sheet for a detailed breakdown of the pros and cons of pervious pavement, or visit perviouspavement.com for more information.
• Detention ponds are most often used to manage stormwater in residential areas and employment districts; however, they can enhance streets in many types of places.  Pocket parks, trails, and greenways can be situated adjacent to a detention pond, providing opportunities for recreation and creating a more visually appealing corridor.
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  CH2M HILL
  Opportunities to use LID strategies to supplement enclosed drainage systems are often overlooked or underutilized.  For example, landscaping is often placed higher than the surrounding pavement (e.g. a raised median on a sidewalk or in a parking lot), thus limiting its ability to absorb runoff, as in the image at right.

The images at right illustrate two simple LID strategies.  In the first image, a downspout from the roof above is channeling rainwater directly into the landscaping instead of directing it through an enclosed stormwater management  system. 

Credit: East-West Gateway

This strategy reduces stormwater capacity requirements while helping to sustain the aesthetically and ecologically beneficial landscaping.  However, the curb and gutter system used for the landscaping island prohibits stormwater flowing across the surrounding impervious surfaces from being absorbed by the landscaping.

Placing intermittent curb cuts around the island, as shown at right, allows some rainwater to flow from the parking lot into the landscaped area for absorption.  Eliminating the curb and setting the landscaped area lower than the adjacent pavement would allow even more stormwater to permeate the natural surface, further minimizing stormwater capacity requirements. 

These simple, effective LID strategies can have significant environmental and economical benefits if applied consistently and appropriately in developed areas.

LID State of the Practice Example: 12th Avenue Green Street Project, Portland

The 12th Avenue Green Street Project in Portland, Oregon is a fantastic example of the successful use of LID stormwater management techniques.  The American Society of Landscape Architects recently awarded the project a General Design Award of Honor (2006), and stated that the project was “…the best example of this type of work we’ve ever seen.”

Credit: City of Portland/ASLA

The initiative was part of a street retrofit project started in 2005.  The project uses stormwater planters to collect, treat, and distribute stormwater from the street, bypassing the existing enclosed drainage system.  The planters aesthetically enhance the streetscape, while providing excellent stormwater management, as shown at right 

For more information about the project, visit the 2006 ASLA Professional Awards Page.

Bicycle-Friendly Design Considerations:

Because bicycles are typically expected to use the rightmost edge of the travel lane (a bike lane, paved shoulder, or wide outside lane), they may encounter various obstacles, such as manholes and grates, which are commonly used along the curbside as part of enclosed drainage systems.

It is important to consider the needs and safety of bicyclists when planning the location and design of these items.  Bicycle-friendly grates and manhole covers should be used along established bicycle lanes and routes, but should also be considered in areas where the potential for bicycle traffic exists. 

Read more: Stormwater