Parcel-level Measure ofPublic Transit Accessibility

to Destinations

Brian H. Y. LeeUrban Design & PlanningUniversity of Washington

19 Nov 2004TransNow Student Conference

Portland State University

Outline

+ Problem

+ Current solutions

+ Proposed method

+ Test case

+ Final words

Public Transit Accessibility

+ Fundamentally differentmode of urban transport

+ Complex spatial &temporal components

+ Multi-modal,walking

Measurement Approaches

+ Access to & frompublic transit network

+ Spatial focus

+ Zonal aggregation (e.g., TAZ)

Implications

+ Exaggerate benefits

+ Incomplete picture

+ Estimations & forecastsevaluations & policies

Current Techniques

+ Area buffers(400m radius)Area ratios

+ Network buffersBedroom ratios(Zhao et al., 2003)

1. Stop & Station Catchment:

Current Techniques, cont.

2. Accessibility to Destinations:

+ Most gravity-based

+ Zonal approach

+ Broad categoriesof destinations

Conceptual Framework

+ Classification of land uses

+ Total travel time

+ Single type of destination orCombination of different types

+ E.g., accessibility togrocery stores

Measurement process

(A) Identify destinations

(B1) Identify all stops (within 400m)

(B2) Calc. walk time from each stop

(B4) Calc. avg. wait time at each stop(1/2 headway)

(B5) Identify all accessible parcels(within 400m)

(C1) Identify all accessible parcels

(within 1,000m)

(D) Choose min. travel time

(E) Associate other data

(B3) Calc. travel time from upstream stops

(B6) Calc. walk access time from parcels

(B7) Sum total travel time(C2) Calc. walk

access time

Transit Walk

Test Case Application

+ King County Metro - Buses

+ One grocery store location

+ Accessibility measurement & population estimate

+ Area buffer & ratio: “Area ratio”

+ Parcel-level – spatial: “Simplified parcel”

+ Parcel-level – spatial & temporal: “Proposed parcel”

Area Ratio Method

Simplifed Parcel Method(res. only)

Proposed Parcel Method(res. only)

Minutes to Destination

0:00 - 5:00

5:01 - 10:00

10:01 - 15:00

15:01 - 20:00

20:01 - 25:00

25:01 - 30:00

30:01 - 35:00

35:01 - 40:00

40:01 - 45:00

45:01 - 50:00

50:01 - 55:00

> 55.00

} 45+ min

Area Ratio Simplified Parcel Proposed Parcel

Census

Tract

TotalPop’n

Estimated Populations Served Ratio

Area Ratio[A]

Simplified Parcel

[B]

Proposed Parcel

[C][A]/[C] [B]/[C]

4400 1,597 142 10 10 14.28 1

4500 923 3 0 0 n/a n/a

5200 3,260 874 396 391 2.23 1.01

5301 8,509 5,558 4,949 4,949 1.12 1

5302 2,528 960 348 348 2.76 1

5802 2,016 3 0 0 n/a n/a

6200 3,800 2,276 3,037 2,974 0.77 1.02

6400 3,201 3,114 2,681 2,631 1.18 1.02

6500 1,511 915 831 788 1.16 1.05

7000 4,744 2,355 2,183 2,131 1.10 1.02

7100 1,809 1,158 1,183 1,183 0.98 1

7200 3,084 2,439 1,483 1,483 1.64 1

7300 2,218 1,653 1,283 1,271 1.30 1.01

7400 8,932 6,838 6,313 6,307 1.08 1.00

… … … … … … …

Total 124,152 71,283 64,301 58,505 1.22 1.10

Percent 100% 57.4% 51.8% 47.1%

Limitations

+ Land use classifications

+ Estimation of waiting times

+ Monetary costs

+ Other transit service characteristics

Conclusions & Recommendations

+ Informative graphical results

+ Realistic (conservative) estimates

+ Potentials for modeling applications

+ Streamline data management & processing

THE END