Dublin's Port Tunnel (DPT) has opened with a toll schedule that is a trucker's dream - heavy tolls on cars and other light vehicles and free passage for trucks over 3.5t (7,716pds) gross weight. Buses with over 25 seats also go free. The toll schedule is skewed to attract trucks and buses to the tunnel while rationing any extra available capacity for the highest value car trips.

Car tolls $15.60 in peak

Car tolls are $15.60 (E12 @1.3 exchange rate) into the city, southbound, mornings 6am to 10am, and out of the city or northbound 4pm to 7pm. Out of peak direction daytime weekday tolls are half that or $7.80 (E6) and night time tolls are $3.90 (E3).

The tunnel is posted with a speed limit of 80km/hr (50mph) and is estimated to provide a 6 minute trip from the port to the M1/M50 interchange compared to 30 to 45min on surface streets.

The official opening was Dec 20 2006 trucks only. With the toll system running the tunnel is open to all vehicles as of Jan 28 2007.

Truck ban to follow

A ban on through trucks 5 axles-or-more using city surface streets 7am to 7pm is to go into effect Feb 19.

Major rationale for the tunnel is improving the efficiency of port operations and getting heavy trucks and buses off surface arterials, while having cars utilize any left over capacity.

The port is right alongside the business and historic center of Dublin at the mouth of the Liffey River. The tunnel at its southern portal has ramps swinging east to the major wharf areas and west to the business district. The northern exit plugs into the tail of the M1 a tight 2x2 lane surface motorway just 2km (1.2mi) before the M1/M50 interchange. The M50 is a C-plan belt route around the Dublin metro area and serves to link the many radial routes coming out from the center of Dublin to all parts of Ireland. It is therefore the major distributor motorway of Ireland.

The Dublin Port Tunnel (DPT) is being designated M50 in an attempt to present it as the easterly end of the belt route.

The tunnel is a twin bore two lanes of 4.5km (2.8mi) length under established parts of north Dublin where acquiring a surface right of way was politically out of the question. For much of its length it is around 21m (69ft) below the surface and at its deepest it is 30m (98ft).

Ireland's National Roads Authority (NRA) claims the DPT is the longest urban motorway tunnel in Europe, though Stockholm's Sodra Lanken or southern link tunnel length is similar (4.6km). The A86W tunnelway under construction in Paris will be 10km (6mi) long.

Hite fight

The tunnel has 3.65m (12ft) wide lanes and 1m (3'4") shoulders each side and a height clearance of 4.9m (16ft), but vehicles are limited to 4.65m (15'3"). There has been fierce criticism of the 4.65m (15'3") by truckers and others, saying greater height was needed to take new 'high cube' trailers 4.88m (16ft) high. The Irish are very strong these days on productivity and competitiveness in trucking. They have truck weights up to the 44t (97k pd) the EU standard (vs US 80k pd or 36.3t). http://www.irishtrucker.com/articles/2003/may/porttunnel.asp

Bridges in Ireland are being built with 5.3m (17'5") clearance, a new EU standard. There's a serious proposal to allow the highcube trailers to operate in certain hours in a single lane down the center of each tunnel section because the circular section would allow this.

[Tell these numbers to New York City where only museum piece miniature trucks are allowed and there is a citywide height limit of 14ft (4.27m) while major trucking routes including interstates have even lower allowed heights I-278 BQE 13'2" (4.01m), I-95 13'10" (4.24m), I-678 Van Wyck Exwy 11ft (3.35m).]

For now overhigh vehicles in Dublin (those over 4.65m or 15'3) will be detected ahead of the tunnel portals and ordered to pull off.

Dropped NATM for TBMs

There are lengthy cut and cover sections at each end of the DPT, and the deep tunnel work in limestone was originally designed to be driven using the economical sequential or New Austrian method with roadheaders, boomers installing rock bolts and shotcrete on reinforcing cage. However a collapse of a sequential method tunnel at Heathrow caused the NRA to go to the more conservative, slower, and expensive tunnel boring machines which install segmental precast structural rings immediately behind the excavation.

Herrenknecht 11.77m (38'7") diameter TBMs were used for the DPT [the largest now in use in the world is a Herrenknecht 15.2m (49'9") in Barcelona Spain.] The segmental lining of this tunnel has an internal diameter of 11.55m (37'9").

The tunnel provides two 3.65m (12ft) travel lanes with 0.25m (10") offsets each side providing 7.8m (25'7") curb to curb. There are raised emergency walkways of 0.85m (33in) each side.

The water table is just below the surface throughout the low flat route so the tunnel is under considerable water pressure.

Forced ventilation is provided by 16 jetfans mounted to the ceiling.

Fire detection systems temperature and optical sensors as well as call boxes at 250m intervals. 100 CCTV cameras provide full video surveillance.

State project, not concession

The tunnel is a project of the Irish state's National Roads Authority financed from the central government budget and the tunnel will be operated on behalf of Dublin City Council. Contracted operator of the tunnel including toll collection is Transroute part of the Egis group of France. Under its contract it will be charging an average $3.8m/yr (E3m) over 5 years with a 2 year optional renewal.

Cost nearly a billion bucks

Dubbed the largest transportation project in the country project cost was $980m (E752m @$1.3=E1) of which construction cost was $580m (E448m). Major tunnel construction was by Nishimatsu of Japan who got a design-build contract in 2000. Work started June 2001. Contract period was 43 months but the work has taken 66 months.

Arup did feasibility studies, Kellog Root and Brown were the NRA technical advisers.

ASCOM tolling

ASCOM designed and installed the toll systems at the toll plaza which is located just south of the southern tunnel portal. There are six toll lanes each direction, all set up for payment of cash to toll collectors (manual), coin machines and transponders. Trucks and buses eligible for free trips have a bypass lane allowing them to travel at the posted speed limit for the whole facility, but all toll collection is single lane, low speed.

Forecast 20k/day total, 8k toll payers

Traffic of about 20k/day with 12k/day untolled trucks and buses, 8k/day tolled cars was forecast in the first year of operation. In the first few weeks of operation with trucks only, traffic has been 6k/day.

Traffic and revenue risk on the tunnel is carried by the state. Tolls are seen mainly as a traffic management tool, not as a financing measure. We haven't so far been able to get any traffic and revenue study.

ADDITION: Spokesman for the project Siobhan Maher tells us: "Prospective tolls are not a factor at this facility, as the main aim is to provide a dedicated ,  toll free route out of the city and Port for heavy goods vehicles and thereby improve the city environment for pedestrians, cyclist, public transport and other motorists. It is not a commuter route and the tolls are set as a deterent to private motorists/commuters."

However he says the forecast toll revenue is $15.6m (E12m) and this will be used mainly to cover maintenance and operations expenses.

Maher says the forecast is for about 21k veh/day total for the first year of which 6k to 6.5k are expected to be heavy trucks (over 17t or 37.5k pd).

BACKGROUND: Dublin City has 1.2m people and the metro area close to 2m or nearly half Ireland's population.

see http://www.dublinporttunnel.ie

TOLLROADSnews 2007-01-29 ADDITION 2007-01-31