23 miles Denver-Boulder toll/transit lane concession sought by Colorado DOT

February 29, 2012

Colorado DOT's tolling arm HPTE has issued an RFQ for a toll concession on 23 miles, 37km of I-25 and US36 Denver-Boulder. The concession is to toll and operate a mix of existing HOT lanes (carpoolers, buses and toll payers), HOT lanes starting construction, and HOT lanes to be constructed under the 50-year concession.

The project involves:

(1) taking over the 7 miles of I-25 EXpress' 2 lanes-reversible operating between downtown Denver and US36 (Pecos St) since 2006

(2) taking over for tolling and operations on 10 miles of single HOT lane each direction plus free-way (general purpose lanes) modernization from I-25 to Interlocken that is being built by CDOT under a separate design-build contract (see sectional diagram below)

(3) adding a single HOT lane each direction for 6 miles of modernization of the existing 2x2 lane free-way between Interlocken and Boulder (see sectional diagram below)

(4) potentially adding HOT lanes on 6 miles of 2x3 free-way lanes on I-25 north from the current end of the operating HOT lanes at US36 going to 120th Avenue a project called I-25 North

With I-25 North HOT lanes it would be 29 miles, 48km to toll and operate.

It involves provision for bus rapid transit, including 5 major park&rides and bus stations, bypass lanes on ramps and some signal prioritization off the expressways.

New construction expected of the concessionaire - in the third portion of US36 Interlocken to Boulder - is estimated to cost in the range $120m to $140m. I-25 North HOT lanes have been envisaged by the state, short-term, as a cheap ($50m) job using a 14ft leftside shoulder each direction, basically a restriping and toll equipment job. However longer term I-25 North might involve more extensive modernization.

On the hallowed ground of the Denver-Boulder Turnpike

Tolls are not new here.

18 miles of US36 opened as a 2x2 lane toll expressway named the Denver-Boulder Turnpike in 1951. It was detolled in 1968. As a Turnpike it had only one intermediate interchange - in Broomfield. Nine other interchanges have been added as development has spread along it, but it remains the original 2x2 lanes.

For 4 lanes, traffic is very heavy at close to 120k average annual daily traffic (AADT) just off I-25 at its southern or eastern end dropping gradually to about 70k near Boulder to the northwest.

I-25 north out of Denver, basically ten GP lanes has over 230k AADt to I-70, then close to 200k north on 8 GP lanes and 180k at US36.

Use of the I-25 HOT lanes is tiny relative to the GP lanes about 3.5m trips/year or just under 10k/day (2010) - about 5% of the total flow. And that is split about two-thirds free carpoolers/transit (6.3k AADT, 2.3m/yr), one-third toll payers (3.2kAADT, 1.16m/yr).

With an average toll for the seven miles of I-25HOT at $2.20 toll revenue has been around $2.4m (2010).

Wilbur/nowCDM Smith has done a traffic and revenue study for the project downtown Denver to interlocken (17 miles on I-25 and US36) without (3) the last segment to Boulder and without (4) I-25 North.

They assume a growth in households in the Denever-Boulder corridor from 205k 2010 to 272k in 2035 and employment from 293k 2010 to 430k in 2035. (Oddly they don't present population assumptions.)

WSA's study projects a hugely greater potential of toll transactions for the US36 HOT lanes than the existing I-25 HOT lanes - for 2015 75k on US36 vs 5k on I-25HOT.

By 2025 they project 10.6k/day toll payers on I-25HOT and 87.1k on US36HOT. This assuming a revenue maximizing toll management policy.

Part of the difference is an artifact of there being a single toll point each direction on I-25 but multiple toll points and therefore multiple toll transactions in a single trip on the US36 portion.

Toll revenue on I-25HOT is put at $3.7m in 2015 - an increase on 2010's $2.4m - rising to $8m in 2025 and $16.8m/year in 2035.

US36HOT toll revenue is put at $2.5m without rampup in 2015 and $1.1m assuming rampup, going to $9.4m in 2025 and $16.8m in 2035.

Adding those toll revenue for the 17 miles Denver to Interlocken on both I-25HOT and US36HOT goes $4.8m assuming US36 rampup, $17.4m in 2025 and $31m in 2035.

Assumes no extra capacity and revenue maximization tolls

The WSA traffic and revenue study is based on no-extra free lanes capacity and on revenue maximization pricing - which will set a toll rate higher and cause HOT lane volumes to be somewhat lower than those which minimize overall congestion and maximize throughput.

The modeling shows inbound to Denver morning travel times growing 2015 to 2035 from 19 minutes to 21 minutes in the HOT lanes and from 26 minutes to 35 minutes in the free lanes. The time savings doubles from 7 minutes to 14 minutes 2015 to 2035 from using the HOT lanes peak hours mornings.

Going home outbound from Denver in the direction of Broomfield (and Boulder) the modeling suggests 2015 travel time of 17min in the HOT lanes, and 34min in the free lanes, already a 17min time savings. But they forecast a continued 17min trip home in 2035 but a 47min trip in the free lanes for a huge 30min difference.

There is strong and increasing commuter traffic to jobs in Boulder (outbound) and even now in the last segment to be built (Interlocken to Boulder the predominant commuter flow is outbound mornings and inbound toward Denver evenings.

Policy risk

The modeling's reliability is heavily dependent on growth assumptions and on policy responses to congestion.

Is extra capacity built as congestion increases, and is that tolled or free?

The RFQ doesn't spell out policy or even assumptions on any of that, so apparently it is being left up to the concession bidders to propose. They'll need to think through what is the most viable strategy, politically as well as financially.

The procurement is being managed by CDOT's High Performance Transportation Enterprise (HPTE) and is their first toll concession.

The RFQ mentions the possibility there may be some government subsidy required contractually to make the project viable.



A presentation on the project:


The project has federal permits and approvals


WSA traffic and revenue study Feb 2011:


The study was produced by WSA which has since been absorbed into CDM Smith.

TOLLROADSnews 2012-02-28

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