Phoenix to Tempe Trunk Line

For a street-running light rail line, Valley Metro rail outperforms. Of US street-running light rail systems, it’s 2nd in ridership per mile of track behind Houston. Houston has over 2x the jobs of Phoenix within a mile radius of downtown (170k vs 80k), and Phoenix should try to replicate that job density to increase transit ridership.

In concert, Valley Metro should make the light rail faster and more reliable. The travel time ratio of transit versus driving has a direct correlation with mode share. Valley Metro should follow the trajectory of Boston’s Green Line light rail, the trunk portion of which became the first subway in the US when it was grade-separated.

The best corridor for an off-street trunk would connect downtown Phoenix, Sky Harbor, and downtown Tempe. Luckily, the right-of-way already exists: with only a $500m capital investment, we can halve the transit trip time between 3 of the region’s largest, densest, most parking-limited job centers.

Rail would be the fastest way to get between Phoenix, Sky Harbor, and Tempe

Today, train speeds are limited by the speed limits of the streets they run on and limited transit signal priority still leaves many trains waiting behind red lights. With a grade-separated right-of-way and minimal intersections—all with traffic preemption and none with traffic volume concerns—trains could consistently reach 55mph.

With a trunk this fast, for select trips transit becomes the fastest option, period.² People who live in one downtown and work in the other, ASU students who would otherwise take the ASU shuttle between campuses, Suns fans using a park & ride to avoid traffic, business travelers getting between the airport and the convention center.

The utility of fast transit will convince some people living in downtown Phoenix to go car-free, some families to keep 1 car instead of 2, and many more to take transit to the airport for vacation. In turn, the trunk will directly and indirectly lead to significant ridership increases and make transit a more important part of the Valley of the Sun’s transportation infrastructure.

A rapid transit trunk between downtowns means better transit and more ridership metro-wide

This new transit trunk will benefit virtually all rail transit trips and trips between the east and west valleys with faster, more reliable service:

• With easier access between the east and west valley, transit riders are able to take new jobs and create new transit trips
• Bus lines feeding the rail, especially near the trunk, will see increased ridership and transfers
• Riders on all parts of Valley Metro rail see improved service reliability because trains never get stuck behind traffic lights on the trunk
• Trunk service is inexpensive to operate, because faster trip times mean an operator can cover more distance in the same time, meaning resources can be spent elsewhere
• More office and residential developments will locate near rail stations, and their inhabitants will be more likely to use rail, contributing to ridership increases

The perfect rapid transit corridor means easy, inexpensive construction

The Union Pacific corridor is well suited to light rail construction, and to shared freight and transit operations. Some existing track can even be saved. A preliminary plan is below. Valley Metro will need to negotiate with UPRR, but it has leverage: projects like the 24th St overpass or Grand Canal grade separations, potential rail crossing closures, new freight tracks.

The corridor generally has enough room for transit and freight tracks to be separated by 50 ft (UPRR’s preferred distance, p L2). Even if UPRR installed a continuous second freight track, there could generally be 33ft+ of separation. That’s more than LA Metro’s 20ft negotiated with UPRR recently for the West Santa Ana Branch (via X), or between Valley Metro and the same UPRR line in downtown Tempe, ~25ft with no crash fence. More examples of and info on shared transit and freight rail corridors.

This rapid transit trunk can jumpstart more Valley Metro projects

Here’s how we can start

1Safeguard rights-of-way⁵
~6.7ac will need to be acquired from private owners. Most importantly, the parking lots between Chase Field and 1st Ave, much of which could be redeveloped after project completion. Parcels of interest are shown on this map.

2Add to Valley Metro’s Capital Improvement Program
This trunk line will benefit virtually all other transit improvements in the region, so it should be a priority project.

3Reroute the I10 extension with the trunk in mind
The mostly grade-separated rapid transit corridor along I10 west deserves fast access to the trunk line and the east valley. Rather than a slow crawl on street-running tracks west of downtown Phoenix, the line should enter downtown along the I10, serve Roosevelt Row, and join the trunk line to the east valley. If not possible in the initial I10 extension project, add provisions for later construction.

Footnotes

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1 Travel time estimate: average alternative 2 travel time between Mill Ave/3rd St and Chase Field/3rd St estimated to be 11m 49s, 1.95x faster than existing light rail. Additional schedule padding may need to be added to this estimate. Full estimated travel time matrix below:

		Existing EB	Existing WB		Alt 2 EB	Alt 2 WB	Avg % improved		Alt 1 EB	Alt 1 WB	Avg % improved
Mill Ave to 44th		9m 34s	10m 34s		5m 13s	5m 11s	194%		5m 30s	5m 24s	185%
44th St station		26s	26s		26s	26s			26s	26s
44th to 3rd		12m 30s	12m 30s		6m 10s	6m 12s	202%		6m 17s	6m 20s	198%
3rd St station		26s	26s		26s	26s			26s	26s
3rd to DT Hub		2m 34s	2m 34s		1m 46s	2m 0s	136%		1m 46s	2m 0s	136%
Total: Mill Ave to Chase Field		22m 30s	26m 30s		11m 49s	11m 48s	195%		12m 13s	12m 10s	189%

Assumptions: Speeds based on curves and other speed limit attributes of designed alignments, listed on click here. Assumes 4″ superelevation where possible and 2″ unbalanced superelevation, based on desirable upper limits from Valley Metro LRT Design Criteria Manual (p18). Assumes 3mphps acceleration and deceleration and 55mph top speed based on maximum operational characteristics of Valley Metro’s old and new light rail vehicles. Assumes station dwells of 26 sec based on average station dwell data collected Fall 2024. Existing light rail travel times are a synthesized average of Google Maps and Valley Metro schedule data accounting for each each interstation and route timing as a whole.

A similar diagram in ADOT’s Passenger Rail Corridor Study (p77) mirrors the findings above. It calculates 8 min travel time between Phoenix Union Station and Sky Harbor, and 6 min travel time between Sky Harbor and Tempe assuming diesel-electric engines and including station dwells.

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2 Travel time comparison: 17 min drive versus <12 min proposed light rail ride between Mill Ave/3rd St and Chase Field/3rd St. More example trip approximate comparisons below:

Example trip	Stations	Existing rail	Proposed rail	Drive time assuming no traffic	Fastest mode?
Downtown hopping, now drawn closer together	Mill Ave/3rd St to 3rd St PHX	23m	12m	17m	Rail
ASU student traveling to DTPHX campus	University/Rural to Van Buren/Central	34m	22m	30m via ASU shuttle*	Rail (vs ASU shuttle)
Suns fan using a park & ride to get to a game	Price 101/Apache to 3rd St PHX	42m	28m	19m	Depends on gameday traffic
Convention visitor arriving from the airport	Term. 4 Sky Train to 3rd St PHX	26m†	15m‡	12m	Depends on traffic, rail freq., ridehail availability

* Other considerations: ASU Maroon shuttle boards on the other side of Tempe campus. Light rail is more frequent, has longer hours, and is likely more reliable. Both are free to ASU students. The same route would be a 17 min drive in a car. If ASU can rely on light rail for transport between campuses, there may be a chance of getting funding for improvements or operations from them.

^† Existing rail assumes 5 min Sky Train ride, 5 min transfer, 3 min wait (based on Sky Train frequency of 5 min), and 13 min light rail ride

^‡ Proposed rail assumes alternative 2c, including a new Sky Train station: 4 min Sky Train ride to new station, 2 min transfer, 3 min wait (based on Sky Train frequency of 5 min), and 6 min light rail ride

Existing light rail travel time calculated via Google Maps. Proposed light rail travel time synthesized from Google Maps and from alternative 2 in the above method. Drive time calculated via Google Maps, assuming no traffic.

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3 Access estimate: The trunk line increases jobs and people accessible within the same transit trip time. The following estimates are underestimates, because ASU is not counted as a “workplace” for students, and ASU students without a job are not included in the population count, among other approximations listed below:

	Veteran’s Way/College	Van Buren/1st Ave	Sky Harbor/44th Street†	Chase Field/3rd St†
Jobs within 30 min on transit: existing	259k	274k	363k†	254k†
Jobs within 30 min on transit: alt 2b	364k	380k	461k	391k
% increase accessible jobs	141%	139%	127%†	154%†
People* within 30 min on transit: existing	78k	68k	79k†	40k†
People* within 30 min on transit: alt 2b	89k	85k	98k	77k
% increase accessible people*	115%	125%	125%†	193%†

To estimate access: isochrones from Travel Time—assuming existing Nov 2024 transit service, then combining isochrones for each proposed station (assumes alt 2b) with estimated interstation timing—were mapped onto 2022 US Census job and population* estimates from OnTheMap.

Estimates are approximate:

• ASU is not counted as a “workplace” for students, and ASU students without a job are not included in the population count
• Existing access estimates overestimate access from north of the DTPHX Hub, because Nov 2024 service doesn’t require a transfer between N-S and E-W lines, whereas soon that transfer will be necessary until the trunk is constructed
• Proposed access estimates slightly overestimate access from east of Mill Ave, because they don’t account for an added transfer to the streetcar for access to stops between Mill and Sky Harbor
• Combining isochrones with estimated interstation timing does not exactly reflect transfer times between rail and other modes.

* “People” refers to the home address of people working in the state. Notably, this excludes ASU students who don’t work in addition to being a student.

^† Existing measurements come from existing stations (44th St/Washington and 3rd St/Jefferson), whereas proposed come from proposed location of trunk stations. This undercounts access with the trunk, because trunk stations are in addition to, rather than replacing, existing stations.

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4 Cost estimate: Alternative 2 is estimated to cost $499m, not including contingency, ~6.7ac of land acquisition, or any compensation necessary to Union Pacific outside replacing infrastructure:

	LRT trunk alt 2a	LRT trunk alt 1	Streetcar across Mill Ave Bridge
Total cost (inflation adjusted)	$249m	$262m	$29m
Cost per mi (inflation adjusted)	$32m/mi	$34m/mi	$37m/mi
Total cost (inflation + transit costs increase adjusted)	$499m	$523m	$59m
Cost per mi (inflation + transit costs increase adjusted)	$64m/mi	$67m/mi	$74m/mi

See the allocations and adjustments broken out by standard cost category here. Here’s how cost estimates were derived:

1. Cost categories: cost per unit calculated for each of the FTA’s standard cost categories based on Valley Metro’s initial operating line using the FTA’s Capital Cost Database
2. Manual adjustments: itemized costs were adjusted where noted here to account for different contexts
3. Inflation adjustment: costs were scaled to account for inflation, from 2008 to 2024, using the BLS’s CPI Inflation Calculator
4. Transit costs increase: costs were scaled again by 200% to account for higher construction costs on recent transit construction projects in the US generally. 200% was chosen as approximate based on more recent Valley Metro project costs per mile (Central Mesa Extension, South Central Extension, Northwest Extension Phase II), adjusted down from an actual increase ~250% due to extension projects being more complex or including more bridges per mile than the initial route. More details here. Costs are shown before and after this multiplier.

In addition to the above, estimates do not include:

• Moving sidewalk connection to Sky Train (Alt 2b) or new Sky Train station (Alt 2c)
• Potential future stations: Trunk at Center Pkwy, Trunk at Phoenix Rising Stadium, or Washington/Jefferson streetcar infill stations
• Related projects: Ped/bike/service vehicle over/underpasses at rail/canal crossings, 150 ft trench through Sky Harbor, 24th St grade separation, etc.

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5 Right of way acquisition and negotiation: In addition to negotiating with Union Pacific for use of its corridor, this proposal requires ~6.7ac of private land and some coordination between government and quasi-governmental organizations. Requirements are listed below in order of importance (parcels of interest are shown here):

1. Use of Union Pacific’s existing rail corridor
2. All of 7 parcels, all currently surface parking, totaling 3.08ac, well over half of which acreage can likely later be redeveloped
3. Portions totaling ~.29ac, all currently surface parking, from 2 parcels totaling .86ac
4. Slivers of 7 parcels totaling 3.29ac (alt 2) or 3.33ac (alt 1), which should not require removal of any buildings
5. Shared use of the fire lane south of Chase Field, currently owned by Maricopa County
6. Vacant slivers (alt 2) or portions of surface parking (alt 1) on 2 parcels of airport land, currently owned by the City of Phoenix.
7. Vacant slivers of land on 5 parcels currently owned by AZDOT, SRP, and the City of Tempe. A small, vacant portion of a 6th parcel owned by SRP would be used for the streetcar extension across Mill Ave Bridge

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6 Cost comparison: Alternative 2a is estimated at around 25% the cost/mi of the two most recent Valley Metro extensions. Comparisons are approximate: trunk line estimate excludes right of way and contingency.

	Cost (year built)	Cost (2024)	Cost/mi (2024)	Cost/mi compared to initial segment	Notes	Alt 2a cost/mi comparison
Initial Light Rail Segment	$1,315m (2008)	$1,888m	$96m	100%		67%
Central Mesa Extension	$197m (2013)	$265m	$86m	89%	Expect much less expensive per mi: likely wider roads (less expansion necessary) with fewer utility issues; no bridges; fewer intersections/stations per mi	75%
Northwest Extension Phase II	$401m (2023)	$413m	$258m	269%	Expect much more expensive per mi: far more aerial/mi and an elevated station; likely more stops/mi	25%
South Central Extension	$1,345m (2023)	$1,385m	$252m	263%	Expect a bit more expensive per mi: no new bridge across the Salt River necessary but work required on RR underpasses and more work downtown/with track in operation per mi	26%
Trunk Line Alt 2a Estimate	~$499m (2024)	~$499m	~$64m	200% then adjusted		100%
Est. high end Scottsdale/Rural BRT	$600m (2021)(p59)	$694m	$45m		Not used to estimate transit costs increase, only for comparison between potential projects competing for funding	143%

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7 Commuter rail comparison: Commuter rail is not a substitute for this project. In fact, this project is a great beginning step toward a regional rail system. Here’s what makes an LRT trunk a better project than commuter rail:

• Better served destinations: Commuter rail would serve the edges of downtown Phoenix, downtown Tempe, and ASU. Light rail already serves the hearts of downtown and midtown Phoenix, Tempe, and ASU and has the potential to serve many more centers.
• Immediate large impacts: A light rail trunk would immediately benefit tens of thousands of existing and new transit riders with faster, more reliable, already frequent service. Commuter rail would begin by serving mostly low-density suburbs via park & rides with virtually no existing transit ridership.
• Lower startup costs: Though light rail requires dedicated tracks, it would still be less expensive than the track modifications, stations, and park & rides required for a first phase of a commuter rail network. Those extra tracks also allow for frequent service, a prerequisite of high-ridership transit.
• Additional capacity: Riders on other parts of light rail would benefit not only from faster trunk service, but also from more than double the capacity on the grade-separated trunk, allowing for more frequent service on future branches.
• Future possibilities: A light rail trunk could be extended into new frequent regional rail lines on rail corridors. The trunk project is probably the best first step toward regional or commuter rail, even if setting aside the benefits that would come with improved light rail.