How Many of the 29,000 Daily Journeys Would Actually Use a Strangford Bridge?

One of the stock lines we hear from DfI officials is this:

“You have no proof that anyone from the wider traffic corridor would use a bridge. All we know is how many vehicles use the ferry today.”

On the surface that sounds reasonable. In reality, it’s a way of dodging some very awkward numbers in DfI’s own traffic counts.

Let’s walk through it in plain English.

The 29,000-vehicles-per-day corridor

Using DfI’s AADT (Average Annual Daily Traffic) counts on the roads feeding the Narrows, we can build up a picture of how busy the Strangford–Portaferry corridor actually is today.

Three key count points tell the story:

• A20 at Kircubbin (Portaferry Road, Ards Peninsula):
  around 7,000–7,500 vehicles per day in recent years.
• A22 at Comber (Comber–Killyleagh Road):
  around 9,000–9,500 vehicles per day.
• A7 at Quoile Bridge, just outside Downpatrick:
  around 12,000–13,000 vehicles per day, with a clear upward trend.

Put those together and you get roughly:

≈ 29,000 vehicles per day moving along the cross-peninsula corridor on the three main arms leading to and from the Narrows.

This is the “real” traffic picture on both sides of Strangford Lough. Thousands of vehicles every day going:

• Downpatrick / Newcastle / Ballynahinch side
  ↔
• Ards Peninsula / Newtownards / Bangor / Belfast side

Now compare that to the ferry.

The ferry is not “demand” – it’s a throttled pipe

DfI and local media usually quote ferry usage in the range of 600–700 vehicles per day.

Set that beside the corridor figure:

• Corridor traffic on the three approach arms: ~29,000 vehicles/day
• Ferry traffic actually crossing the Narrows: ~650 vehicles/day

That means:

Only 2–3% of the traffic in the corridor is using the “direct” A2 link across the Narrows.
97–98% are being forced round the long way.

So when DfI say:

“Only 600–700 vehicles per day use the ferry, therefore there is no demand for a bridge”

they’re doing something very misleading:

• They are treating ferry patronage as if it measured underlying demand,
• When in reality it measures how many people are willing to pay a fare, wait for a boat, put up with queues and cancellations – despite having a 47-mile alternative.

The true demand is reflected in the 29,000 vehicles using the surrounding network, not the tiny fraction squeezed through the car deck of a small vessel.

So what % of those 29,000 would actually use a bridge?

We have to be honest here: we don’t have full origin–destination data, and we don’t pretend that all 29,000 would pile onto a bridge on day one.

But we also don’t need to guess wildly. We can use the same kind of logic DfT and DfI use in every other road scheme appraisal: time, cost and catchment.

1. Time saved

The current road alternative between the two sides is roughly a 47-mile detour via Comber and Newtownards (or via the A1/Ballynahinch for some journeys).

A fixed link over the Narrows would typically:

• Cut out 45–60 minutes of driving on a cross-lough trip
• Replace it with perhaps 10–15 minutes including the approach and crossing

For a commuter, a tradesperson, or a delivery driver, that is a huge saving. Transport economics 101 says: if you offer people a reliable way to save almost an hour each way, a significant share will take it.

2. Generalised cost (time + fuel vs toll)

In official transport models, the key quantity is “generalised cost” – essentially:

Time cost (valued in £ per hour) + fuel/vehicle costs + any toll/fare

If we plug in conservative values:

• Value of time for car users: roughly £6–£10 per hour
• 45–60 minutes saved each way = £4.50–£10.00 of time benefit per trip
• Fuel and wear-and-tear on 47 extra miles: easily £4–£5 each way for a typical car

That means a bridge user could be saving:

Around £8–£15 per crossing in total time + fuel cost, compared with the long detour.

Even if there was a £3–£4 toll, most users would still be significantly better off every single trip.

So the idea that nobody would switch to that cheaper, faster option – that we’d have 0% diversion – is simply not credible.

3. Who actually benefits? (The “bridge-relevant” pool)

We don’t claim all 29,000 vehicles per day are a realistic market for the bridge. Some are purely local trips that don’t cross the lough at all.

But if you draw a sensible catchment:

• On the Downpatrick side: Downpatrick, Ballynahinch, Newcastle and surrounding villages
• On the Ards/Belfast side: Portaferry–Kircubbin–Newtownards–Bangor–east Belfast belt

…it’s reasonable to assume that a significant slice of those 29,000 vehicles are making journeys that would genuinely be shorter via a Strangford bridge.

To keep things cautious, assume:

• Only 40% of traffic on the A7 Quoile and A20 Kircubbin arms, and
• Only 20–30% of A22 Comber traffic

are making trips that could be meaningfully shortened by a bridge.

That gives a “bridge-relevant” pool of perhaps:

10,000–15,000 vehicles per day
(a fraction of the 29,000, but still a very large number)

Now apply modest diversion rates to that pool:

• Low scenario: 30% switch to the bridge
• Central scenario: 50% switch
• High (but still realistic): 70% switch

You get something like:

• Low: ~3,500 vehicles per day on the bridge
• Central: ~5,800 vehicles per day
• High: ~8,000 vehicles per day

As a share of the total corridor flow (29,000), that’s roughly:

Around 10–25% of existing daily traffic using the bridge,
even on cautious assumptions.

Importantly, this is not new traffic conjured from thin air. It is existing traffic, currently forced to waste fuel and time on long detours, being allowed to use a rational, direct route. Consider the climate implications !

Comparators: what happens elsewhere when you fix a bottleneck

DfI may claim, “Well, that’s your opinion. How do we know people really change behaviour like that?”

We don’t have to look far:

• When the Skye Bridge replaced the ferry, traffic on the crossing rose significantly above national background growth – even when there were tolls. Once tolls were removed, it rose further.
• The ongoing Corran Narrows fixed link work in Scotland assumes multiples of existing ferry traffic once a bridge/tunnel is in place, precisely because of time and reliability benefits.
• When tolls were scrapped across the Severn in 2018, traffic volumes jumped by around a third in a few years. People respond – quickly – when you remove a barrier.

In all of these cases, the idea that “nobody will change their travel pattern” would have been laughed out of the room.

There is no reason Strangford would be the only exception on these islands where human behaviour and basic economics stop working.

Why DfI’s “0% diversion” argument fails

DfI’s implicit line is:

“We only have proof that 600–700 vehicles/day use the ferry.
We therefore assume 0% of the wider 29,000/day corridor traffic would use a bridge.”

That is not a neutral or cautious assumption. It is a political assumption dressed up as technical caution.

It ignores:

• The huge time savings a bridge would offer
• The big reduction in fuel and operating costs
• The proven experience from other replaced ferries and improved crossings
• The existence of a 29,000-vehicles-per-day corridor right on the doorstep of the Narrows

A genuinely neutral, evidence-based position would be:

• Identify the bridge-relevant catchment
• Run a standard DfT/DfI transport model with time, cost and elasticity assumptions
• Test low, central and high diversion scenarios (e.g. 10%, 20%, 30% of the corridor)
• Publish the results

Until that is done, the claim that no one would change behaviour is just that – a claim.

The simple truth in one paragraph

In the end, the picture is very simple:

There are about 29,000 vehicles every day on the main roads feeding the Narrows.
Only about 650 of them make the direct crossing on the ferry.
The rest are forced into a 47-mile detour that wastes time, fuel and money.
If you replace that bottleneck with a fast, reliable bridge, it is not realistic – or honest – to pretend that 0% of those 29,000 journeys would switch.
Even using conservative assumptions, you end up with several thousand vehicles per day choosing a Strangford bridge.

That is the core message DfI will struggle to refute, because it flows directly from their own traffic counts and from basic transport economics, not from wishful thinking on the Ards Peninsula.

Persistence !