The Portland, Oregon/Vancouver, Washington Metropolitan Area is in the process of developing a regional rail system. The original 15-mile-long (24-kilometer-long) Banfield, or eastside Metropolitan Area Express (MAX), line went into operation in 1986. It has been embraced by the region as a success. The next extension, 18 miles (29 kilometers) to the westside, will be operational by 1998. PB is the lead facilities design and construction management firm for that extension.

Figure 1: "Columbia River" Four Photographs Stitched Together

Figure 2: Layering Technique Used in Adobe Photoshop

Figure 3a: Stimulated Concrete Segmental Alternative.

Figure 3b: Simulated Bow String Arch Alternative.

Figure 4: Example of 5-Minute Walk Network for a Proposed LRT Station. Figure 5: Example of 5-Minute Walk, Isochron Based on Walk-Network Shown in Figure 4.

A 20-mile (32-kilometer) south/north transit corridor will extend the regional rail system as a bistate project. Portland Metro, the Regional Metropolitan Planning Organization, is preparing the Draft Environmental Impact Statement and Tri-Met, the Tri-County Metropolitan Transit Agency, is initiating preliminary engineering. PB is the lead consultant for preliminary engineering.

We have provided a number of innovative ideas to date, including developing criteria and visual simulations for major river crossings and using geographic information system (GIS) technology to delineate areas within which pedestrians can access a station within a given amount of time.

Visual Simulations of Major River Crossings

The project will include transit bridges between 2,000 and 4,000 feet long (610 and 1220 meters). These bridges would need to meet requirements for navigation clearances and urban design with a cost-effective solution, and they would affect the visual and aesthetic aspects of the community.

We led a bridge workshop to provide the affected agencies with a better understanding of issues associated with major river crossings, in particular one at the Columbia River adjacent to the existing I-5 bridges and one at the Willamette River just south of downtown Portland.

We prepared visual simulations of candidate bridge types that had been identified at the workshop to portray how these could look if constructed. Then we selected and photographed several key views that were of particular concern to the community. Because of the length of the LRT crossings, multiple photographs were “stitched” together electronically to produce seamless panoramic views (Figure 1).

We used Autocad to create 3-dimensional computer models of each bridge type, then view-matched the models over each corresponding panoramic view. We were able to match perspective, scale and location of each alignment by using camera lens information and shoreline data. We also added realistic color, texture, shade and shadow. Each element of the simulation is stored electronically on layers (Figure 2) so any changes of the various color and texture schemes can be done quickly and cost effectively.

Alternatives were generated in Seattle and, via PB’s wide area network (WAN), were reviewed several hours later in Portland. The success of these simulations was measured by the realism and ease of which they communicated conceptual designs to the public (Figures 3a and 3b). The processes involved interdisciplinary coordination between several PB groups—the Portland project team, Seattle structures group, the major complex bridges service center and 4-D Imaging.

Analyzing Transit Station Accessibility with Walk Isochrons

Using an innovative geographic information systems (GIS) methodology, we worked with the client to evaluate pedestrian accessibility of 36 potential transit stations. We used Arc/Info GIS software to modify an existing digital street database to include all appropriate pedestrian connections between potential stations and surrounding development. Travel distance was determined by using an average walk speed modified to account for the stairs, slope, traffic signals and street width.

We used GIS to determine the street links accessible within a 5- and 10-minute walking distance from each potential station (Figure 4). “Walk isochrons” were then developed by creating polygons that enclosed these links (Figure 5). This information was transferred to the client, who estimated potential ridership for each station by overlaying the walk isochrons onto population and employment databases. These data were used to estimate the number of transit trips for each potential station and to evaluate the feasibility of different station locations and of different light rail alignments. By using GIS, we created a powerful method for modeling pedestrian behavior and forecasting ridership.