Pedestrian Infrastructure on the Public Right-of-Way: Aging Pedestrians and Prioritizing Sidewalk Hazards Using the Ultra Light Inertial Profiler (ULIP)

Khambatta, Arfaraz

Sally Swanson Architects, San Francisco, California

Loewenherz, Franz

City of Bellevue, Bellevue, Washington


SUMMARY
Walkability is an important criterion of livable communities and has been tied to health and social benefits. New planning concepts reducing car dependency will increase senior resident’s time on sidewalks. While cities are required by ADA laws to reduce sidewalk hazards, the time and cost of gathering exact data has been a deterrent. The typical sampling of elements such as sidewalks, curb ramps, pedestrian crossings, and obstructions do not provide an adequate understanding of the hazards and barriers throughout a district. In particular, prioritizing the most critical sidewalk hazard locations for city maintenance is not organized and tied to other street maintenance plans. A new and innovative tool, the ULIP, developed through the Federal Highway Administration, allows 100% sidewalk inventory and converts the data into a city’s GIS system. Knowing exactly the location and severity of sidewalk barriers increases the likelihood that all hazards are addressed, reducing the potential for falls and accidents. This innovative technology is now being tried in five cities. In the future, time and cost savings could be accrued, treating ADA code requirements on a regional rather that a city scale. As cities plan for greater sidewalk use by a new generation of aging residents, they can reduce potential accidents and the possibility of increased litigation.

Key Words:accessibility; ULIP; right-of-way; aging; pedestrian

PURPOSE OF THE STUDY

Information on new methods of eliminating sidewalk barriers

MATERIALS AND/OR METHODS

Research, interviews, and data from pilot study in the City of Bellevue, Washington.

RESULTS OR EXPECTED RESULTS

More informed decision-making on methodology of removing sidewalk barriers

DISCUSSION

1.WALKABLE COMMUNITIES

Livable communities are walkable communities; the two go hand in hand.Decreasing the time residents spend in their cars and increasing the time they spend walking is a component found on the agendas of city governments to create a better quality of life in their communities. Popular movements, organizational and government campaigns, including New Urbanism (www.cnu.org), the Center for Disease Controls’ Healthy Communities (www.cdc.gov), the American Institute of Architect’s livable communities (www.aia.org) and many others, place a new unprecedented focus on the walking environment.

Many of the requirements for safe and accessible sidewalks already exist as required codes. The Americans with Disabilities Act (ADA) of 1990 provided civil rights protection to those with disabilities; amendments since that time have extended those rights to cover access to services, which includes accessible sidewalks. These code requirements are mandatory for cities and counties to uphold [Americans 2009] although time and budget constraints have often turned compliance into a reactive endeavor through ADA complaints and litigation.

America’s growing senior population has been a spur for the creation of walkable communities. Within 20 years, the US Census Bureau estimates that more than 19% of Americans will be over the age of 65 [National 2008]. The American Association of Retired Persons (AARP), in their definition of livable communities, includes affordable and appropriate housing, supportive community features and services, and adequate mobility options. On AARP’s Evaluation Guide for Livable Communities, walkability is an important element with 20 criteria listed for rating.

Walkability is a key requirement for livable communities because walkable communities have been linked to many health benefits. Studies show that physical activity, such as walking, can extend older persons’ independent life, lower death rates, and reduce costs of health care. Investing money in creating a more walkable community brings large returns in terms of health and social benefits. A report from the United Kingdom [Sinnett 2011] lists walking as lowering death rates by 20%, reducing cardiovascular disease up to 30%, and reducing the risks of high blood pressure and cholesterol, aside from exercise helping to reduce weight. The positive impact on mental health, and social connection to a community, has also been researched [Leyden 2003], as well as it being an alternative that provides a safer mode of mobility to the aging than driving.

In AARP’s livability survey, walkability criteria includes a number of factors, among them are ratings for sidewalk maintenance, appropriate curb cuts and sidewalk obstructions. The need to reduce sidewalk hazards, particularly for seniors, underlies their greater susceptibility to falls. Each year, Americans who are 65 and over fall, and a third of the falls cause injuries requiring medical treatment. The leading cause of injury deaths for those 65 and over are falls and about half of those resulted in traumatic brain injuries [Thomas 2008]. As cities emphasize walking for health and spending more time out of doors, creating a safe walkable environment for seniors becomes critical.

2. THE ULIP

The ADA requires state and local governments to prepare a Self-Evaluation Plan to identify all access issues. Public agencies are required to develop a Transition Plan to identify and schedule the removal of barriers to their programs and facilities. But regularly updating transition plans for pedestrian facilities on public rights of way (such as curb ramps and sidewalks) is challenging.

In the traditional approach, sidewalk measuring is a labor intensive task. One person walks down the sidewalk, placing a level at a prescribed distance, usually every two to four feet, measuring the running slope (slope in the direction of travel), cross slope (slope perpendicular to the direction of travel), and slab-to-slab faulting inventory assessment. On average, measuring covers less than one mile per hour. The many digital images and measurements that result can make assessing compliance difficult when referencing then from a desk at a later point in time.

Due to the high cost, length of time, and complexity of conducting accurate measurements, many agencies find that they cannot feasibly complete a 100% inventory; instead they conduct samplings and extrapolate. Often approximations, the data can also be out of date because budget limitations preclude updating on a regular basis.

A new alternative methodology is based on an inertial profiler system that had been in use since the 1970s to measure defects onhighway andairport pavement surfaces. The Ultra-light Inertial Profiler (ULIP) system was designed and developed by Starodub, Inc. in Kensington, MD, under contract with the Federal Highway Administration, which is responsible for ensuring access to pedestrian facilities within the public right-of-way.

The innovative system, mounted on a Segway HT scooter, has both sensor and data acquisition components. The device’s laser measurement system, three accelerometers, and gyroscope measure the sidewalk profile at a rate of 10,000 records of data per second. Together, these devices enable the capture of highly accurate location-specific information about sidewalk slope and small surface variations that can make a sidewalk difficult to navigate [Starodub 2011]. The accompanying software is compatible with a City’s asset management database and Geographic Information Systems (GIS).

Using the new Segway approach, one person is able to measure, in more detail than the traditional method, six miles of sidewalk per hour. The ULIP is therefore a cost-effective solution for inventorying and mapping the degree to which sidewalks and curb ramps meet ADA standards. Also advantageous is that the ULIP allows 100% data collection rather than samplings, resulting in accurate information for any sidewalk within the measurement boundaries.

3. GIS INTEGRATION

The ULIP uses ESRI ArcPad to automatically record the exact position of access barriers using the inertial navigation system. That information is then plugged into a GIS computer system to store, analyze, compare and display the information. The raw ULIP data is first imported into ArcGIS which turns the surveyed route into a digital rendering.

Once the field data collection and validity checks are performed, the raw data is calibrated and processed so it can be analyzed. The data is associated to GIS layers, each representing one of several characteristics and linked to geographic points. For example, the ULIP measurements are one layer, curb ramps and pedestrian signals would each have a layer as well. GIS is used to overlap the data layers and determine the cumulative intensity of all characteristics throughout the area measured.

3.1 Technical Infeasibility Analysis

Among the barriers measured are those sidewalk areas that are deemed “technically infeasible.” Side walk grades, per ADAAG standards, should not be greater than five percent. But sidewalks follow the existing topography and the slope doesn’t always meet the ADA guidelines. If a City is able to document the issue as technically infeasible because of the existing grade of the adjacent street, it can greatly reduce the amount of non-compliant barriers which the City is responsible for mitigating.

3.2 ADA Activity Ranking

Sidewalk Data Aggregation involves converting all the data from the various sidewalk related datasets into attributes which are then attached to each individual sidewalk feature. This is an intermediate step for barrier ranking and the mapping interface required to create an ADA dataset. When completed, activity scores for each ADA feature are assigned. Pedestrian facilities heavily used are assigned a higher priority for repairs than those which are not as often used. A variety of spatial data characteristics such as socio-economic data, transit routes and stops, arterial classifications, housing and employment density, and others, are used to assess each feature and assign it a score. A key feature of this GIS-based ranking tool is a user-friendly interface which allows City staff to assign different weights to the various criteria and re-run the analysis in order to iteratively refine the analysis as needed.

3.3 ADA Impedance Scoring

Scores are determined for each ADA feature based upon the field data collected. A sidewalk with large portions of non-compliant slope and grade, or with numerous obstructions, would be assigned a higher priority for repairs than one with few issues. User-friendly interfaces allow City staff to adjust weights and try different scoring scenarios to validate the scoring strategy.

3.4 Final Prioritization scoring.

The activity and impedance scores from the above tasks are combined to create the final prioritization score for each feature.

A City then has the option to use the created data layers on their existing computer system or through a GIS viewer where all information could be accessed from a dedicated web page. This browser-based GIS Viewer is a lightweight, fast application which allows for basic viewing and reporting on the ADA dataset through ArcGIS Server web application & documentation. The application’s basic features and functionality:

·  A set of cached base map services such as Bing Maps, aerial photography or similar, with interface for toggling visibility between them

·  A custom cached map service displaying data from the City’s GIS database, such as city limits, landmarks, or similar

·  A dynamic map service showing the ADA data

·  Standard map navigation tools

·  A Table of Contents widget allowing user to turn on or off individual ADA data layers

·  Address search functionality allowing user to enter an address and zoom to it on the map

·  Identify functionality, allowing user to click on an ADA feature to get attributes, photo or hyperlink, etc

Staff training in the use of the barrier ranking tool and browser-based mapping interface would be important to achieve the best results.

4. THE CITY OF BELLEVUE – REDUCING COSTS

The customized ULIP system was implemented through a pilot program in the City of Bellevue. The city has a population of 120,000 residents, with approximately 15 percent living with a variety of disabilities and 13.4 % of the population over the age of 65. In 2006, the City initiated an update to their ADA transition plan documenting existing physical barriers for persons with disabilities. Bellevue considered a number of options for gathering data on its 336 miles of sidewalk and 4,000 curb ramps. Based on preliminary tests using existing options, the City concluded that the cost could be $1 million at a minimum [Loewenherz, 2010].

Hearing about the profiler technology, an interdepartmental City team partnered with federal and regional agencies to adapt it to their needs. In 2006, the FHWA’s Office of Pavement Technology funded Starodub to provide the City of Bellevue with a ULIP and support. Additional FHWA funding was provided in 2007 for software refinements.

Bellevue’s city staff managed a three-agency partnership, including Transportation and IT Departments, to field test versions of the technology,and developed programming to synthesize ULIP data records into the city's GIS system.

King County, a transit operator in the region, provides ADA curb-to-curb para-transit service, used extensively by the elderly. The service is a safety net for those whose disabilities prevent use of fixed route bus service. Bellevue consulted with the Department of Accessible Services to ensure that the ULIP technology would save time and money that would otherwise be spent conducting accessible pathway assessments. King County subsequently provided support for two staff members involved in the inventory process.

The City of Bellevue sought confirmation that data acquired from the ULIP platform was reproducible and accurate as it was a new system. In 2007, during the trial period, Bellevue and Starodub, Inc. staff undertook numerous tests comparing grade and cross slope measurements from the ULIP and alternative measurement devices (e.g., digital smart level readings) before a decision was made to employ this technology citywide. Bellevue testing with global navigationsatellite system (GPS) found the accuracy oflatitude/longitude data degraded in areas with tall buildings or thick tree canopies.After evaluating alternative approachesa sensor-based inertial navigation system integrated with an ESRI ArcPad interface was selected toenhance the accuracy of the spatial datain the inventory. To establish travel pathcontrol points, field technicians enteredthe start and end points for each datacollection run on an ortho-photo image on the ULIP’s notebook computer screen. The gyroscope, accelerometers and distance measurement instrument in the sensorbox were used to compute the ULIP’s relative path of travel. The relative travel pathwas combined with the control points to produce a travel path consistent with thecity’s GIS system [City of Bellevue, 2009]