Michael Lowry

Comparing spatial metrics that quantify urban form

Abstract Measuring and characterizing urban form is an important task for planners and policy analysts. This paper compares eighteen metrics of urban form for 542 neighborhoods in Salt Lake County, Utah. The comparison was made in the context of characterizing three neighborhood types from different time periods: pre-suburban (1891–1944), suburban (1945–1990), and late-suburban (1990–2007). We used correlation analysis, within and across time periods, to assess each metric’s ability to uniquely characterize urban form; and we used linear regression to assess the ability to distinguish neighborhood type. Three of the metrics show redundancy and two did not capture differences in urban form for the case study. Based on our findings, we recommend thirteen of the eighteen metrics for planners and policy analysts who want to quantify urban form using spatial data that are commonly available. Furthermore, our case study shows that despite policy efforts to encourage “smart growth,” urban neighborhoods in Salt Lake County continue to exhibit characteristics of “sprawl.” These findings suggest the effectiveness of smart growth policies in Salt Lake County have had limited effect.

Assessment of communitywide bikeability with bicycle level of service

A novel method assessed the quality of bicycle travel throughout a community. Most previous research on the quality of bicycle travel assessed bicycle suitability, that is, the perceived comfort and safety of a linear section of bikeway. Assessment of bikeability (as defined by authors), however, considers comfort and safety of the entire bikeway network for access to important destinations, and there is ample research concerning the related concept of accessibility. A proposed calculation for bikeability was developed on the basis of a common accessibility equation and was demonstrated through a case study of three capital investment scenarios. The analysis used a geographic information system. Engineers and planners can follow a similar procedure to the one used in the calculation development to prioritize improvement projects or to communicate the benefits of new projects.

What Makes a “Complete Street” Complete? A Robust Definition, Given Context and Public Input

The concept of “complete streets” has gained momentum as a way to make communities more livable. This study presented a novel way to assess completeness, given context and public input. The approach was to use a four-dimensional audit for automobiles, transit users, bicyclists, and pedestrians. Although other assessment methods are intended to evaluate operational performance, this study proposed an audit-based assessment method as a valuable addition for planning purposes. Audit results were plotted on four axes to depict a provision profile to compare the balance between the modes. The most significant innovation was a framework to calculate a completeness score according to a communitys vision for that particular street. Advantages of the framework were demonstrated through a case study in which 67 streets were assessed in a small, rural community. A review of the results revealed that some streets, as the result of the community-defined context, received completeness scores that were better than expected. Public volunteers provided critical input in the case study, and their role is explained in this paper.

Using Origin-Destination Centrality to Estimate Directional Bicycle Volumes

A new method estimates directional bicycle volumes throughout a street network. The method is based on a modified form of centrality, a measure from graph theory used to quantify the relative importance of each link and node in a network. One common formulation of centrality calculates the number of times a link in a network is used along the path of all shortest paths between all nodes. The equation was modified to represent bicycle travel better. The new metric is called origin–destination (O-D) centrality. For this case study, the new metric exhibited high correlation (R2 = .45 to .73) with observed bicycle counts at intersections. Use of O-D centrality to interpolate field observations spatially is demonstrated. Unlike other bicycle demand estimation methods, this approach requires commonly available data, is easy to use, and produces directional volumes (some methods only estimate nondirectional aggregate counts). The new method was programmed as a tool for geographic information systems by using modifiable open-source python code. The tool requires a street network, a digital elevation map, parcel data, and observed bicycle counts at select locations throughout the study area. The observed counts can be collected through any manner, but the tool was specifically designed for planners and engineers working with count data collected manually in a manner similar to that used for the National Bicycle and Pedestrian Documentation Project.

Tools and Strategies for Wide-Scale Bicycle Level-of-Service Analysis

This paper introduces new tools and strategies to assess the perceived comfort and safety of bicycle travel across a large geographic area. The tools are based on the equation for bicycle level-of-service in a U.S. government manual. The equation requires substantial data that can be time-intensive and expensive to collect for a wide-scale area. For this reason, the paper begins by discussing data-availability issues with a survey that was sent to every city and county in Idaho. Of the 115 responses, no community had all the necessary data and many had very little data. Next, the paper describes a sensitivity analysis that engineers and planners can follow to identify the critical data that should be collected for their community. The sensitivity analysis is described using two case study communities and reveals, among other things, that input-output sensitivity for bicycle level-of-service depends on roadway functional class. The tools and strategies in this paper will save communities time and money when developing plans or prioritizing projects.

Regional land use and transportation planning with a genetic algorithm

A new approach to regional land use and transportation planning, which uses a genetic algorithm as an integrated optimization tool, is presented. The approach is illustrated by applying it to the Wasatch Front Metropolitan Region, which consists of four counties in the state of Utah. This genetic algorithm–-based approach was applied earlier to the twin cities of Provo and Orem in Utah, but here it is adapted to regional planning. Three issues make regional planning particularly difficult: (a) individual cities have significant planning autonomy, (b) the search space of possible plans is immense, and (c) preferences between competing objectives vary among stakeholders. The approach used here addresses the first issue by the way the problem is formulated. The second issue is addressed with a genetic algorithm. Such algorithms are particularly well suited to problems with large search spaces. The third issue is addressed by using a multiobjective fitness function in the genetic algorithm. It was found that a genetic algorithm could produce a set of nondominated future land use scenarios and street plans for a region, from which regional planners can make a selection. Execution of the algorithm to produce 100 plans per generation for 100 generations took about 4 days with a high-end personal computer. Interesting trends for reducing change and traffic congestion were discovered.

Quantifying bicycle network connectivity

The intent of this study was to compare bicycle network connectivity for different types of bicyclists and different neighborhoods. Connectivity was defined as the ability to reach important destinations, such as grocery stores, banks, and elementary schools, via pathways or roads with low vehicle volumes and low speed limits. The analysis was conducted for 28 neighborhoods in Seattle, Washington under existing conditions and for a proposed bicycle master plan, which when complete will provide over 700 new bicycle facilities, including protected bike lanes, neighborhood greenways, and multi-use trails. The results showed different levels of connectivity across neighborhoods and for different types of bicyclists. Certain projects were shown to improve connectivity differently for confident and non-confident bicyclists. The analysis showed a positive correlation between connectivity and observed utilitarian bicycle trips. To improve connectivity for the majority of bicyclists, planners and policy-makers should provide bicycle facilities that allow immediate, low-stress access to the street network, such as neighborhood greenways. The analysis also suggests that policies and programs that build confidence for bicycling could greatly increase connectivity.

Using Traffic Simulation Software to Manage Recreational River Boats on Public Lands

This paper describes a novel use of traffic simulation software to model and manage recreational river use. River tourism usually benefits the local economy, but the influx of visitors can also burden the other functions of a river such as agricultural irrigation and critical habitat for flora and fauna. The management of boats on a river is very similar to the management of cars on a freeway. This paper describes how these similarities were modeled with the software package VISSIM. The paper elaborates on the differences encountered, including a discussion about the underlying differences between a traffic engineers concept of capacity and that of a recreational manager. The model was used to evaluate three management strategies for dealing with future growth: (a) do nothing, (b) build and improve boat ramps, and (c) issue limited boat launch reservations. The three strategies were evaluated on the basis of density (boats per mile) and boat ramp delay (excess minutes because of queuing). The input for the model included nearly 600 boats and 1,200 visitors. The results suggest that lower density and delay are best achieved by issuing limited reservations. The paper is intended for managers of public lands who may not be familiar with traffic simulation software. The approach could be extended to the management of other recreation facilities, such as bike paths and hiking trails. The paper is also useful for traffic engineers interested in new perspectives on capacity and congestion.

Practitioner survey and measurement error in manual bicycle and pedestrian count programs

ABSTRACT Manual bicycle and pedestrian count programs that involve community volunteers can be a low-cost means to collect nonmotorized traffic data while providing opportunity for public involvement. The purposes of this study were to investigate why communities are performing manual counts and estimate the degree of measurement error associated with conducting manual counts. An online questionnaire was sent to transportation specialists across the United States. There were 92 responses received from 25 states. Eleven communities were contacted for phone interviews. Information about community volunteers, scheduling and logistics, data collection techniques, and reasons for conducting manual counts were summarized. Some of the reasons cited by the survey respondents for conducting manual counts seem unrealistic and possibly flawed. Measurement error was assessed through a controlled field experiment with 25 counters at five intersections. Lower measurement error rates were observed when using a four-movement data collection technique compared to a more complicated 12-movement technique; however, the differences were not statistically significant. The overall median absolute percent error for the 12-movement technique was 27% and 7% for bicyclists and pedestrians, respectively. The field experiment showed no consistent increases in measurement error when counters were assigned to collect additional information, such as sex of traveler or whether bicyclists wore helmets.