Cyngor Bro Morgannwg
Vale of Glamorgan Council

HG1 KS1 North West Barry (Weycock Cross)
Objection-Transport Assessment – Modelling Addendum’
(Asbri Transport, for Persimmon Homes)
Displayed on OC2 website KS1 as: “Draft Transport Assessment” Filename on same: “Draft TA with Appendices_Redacted.pdf”

Ref: NWB_RLDP_JVN_009: RLDP public consulta on feedback on ‘North West Barry Transport
Assessment – Modelling Addendum (May 2025)’ (KS1 ‘Supporting Informa on’ Persimmon
Homes/Asbritransport report)
This RLDP consulta on feedback focuses on key areas of contradiction between this document
with current transport planning policy (PPW, TAN18 etc).
1. Overall approach: capacity-first, car-first
 Contradiction: focus on junction capacity, not demand reduction or modal shift
The Dra Transport Assessment is almost entirely framed around ratio of flow to
capacity (RFC)/degree of saturation (DoS), queues and “spare capacity” at Weycock
Cross, with success defined as accommodating extra car trips and “marginal and
inconsequential impact” on delay. PPW and TAN 18 require integra on of land use and
transport to reduce the need to travel by car, priori se sustainable modes, and use
demand management rather than simply expanding capacity.
 Contradiction: treating congestion as a problem to be ‘engineered away’
The document repeatedly treats existing conges on as something to be relieved by extra
lanes, slip roads and signalisation, rather than asking whether additional car-based
development at this location is compatible with decarbonisation and modal shift
objectives. PPW/Future Wales emphasise reducing traffic growth and car dependency,
not perpetually enlarging junctions.
2. Treatment of cumulative impact and “inconsequential” language
 Contradiction: downplaying cumulative impact while acknowledging severe future
congestion
The Draft Transport Assessment accepts that with the committed development, traffic
levels at Weycock Cross will be “extreme and unacceptable” and “over capacity”, yet s ll
concludes the site’s impact is “marginal and inconsequential”. TAN 18 and PPW require
consideration of cumulative impacts and whether the network is already at or near
capacity—small percentage increases can still be material where junctions are stressed.
 Selective use of the 5% threshold
The Dra Transport Assessment criticises other TAs for not modelling arms with >5%
impact (quo ng TAN 18 Annex E), but then uses low percentage increases (1.3–3.4%) to
argue its own impact is negligible, despite RFCs >1.0 and acknowledged severe
conges on. That’s internally inconsistent with the spirit of TAN 18, which explicitly notes
that where capacity is or nearly exceeded, even smaller increases are normally material.
3. Junction “enhancements” vs policy on induced traffic and placemaking
 Contradiction: proposing extra capacity (slip lanes, longer lanes, bypass) as primary
mi ga on
The Draft Transport Assessment’s main mitigation is more road capacity: extended left
turn lanes, a free-flow le slip, and signalised junction to facilitate safe site access. PPW
and TAN 18 stress that engineering new road capacity with the sole aim of reducing
conges on can induce traffic and is generally contrary to sustainable transport and
climate objectives.
 No real engagement with placemaking or severance
There is no discussion of how a free-flow slip and extra lanes affect pedestrian/cycle
severance, crossing quality, safety, noise, or place function at Weycock Cross, despite
PPW’s placemaking and “healthier places” requirements.
4. Active Travel: treated as an add-on, not a structuring principle
 Contradiction: Active Travel framed as a by-product of a signalised access
The Dra Transport Assessment presents “dedicated demand dependent green me for
pedestrians and cyclists” at the new signals and a link to the proposed Active Travel
route as a benefit, but only as an adjunct to a junction designed primarily for motor
traffic. The Active Travel (Wales) Act and PPW require that walking and cycling are
prioritised in scheme design, with high-quality, coherent routes and minimal delay—not
simply accommodated within a car-optimised junction.
5. Location and land use integra on
 Tension with accessibility and car-dependence tests
The Draft Transport Assessment does not really test whether this greenfield, edge-of
Barry site can support a genuinely sustainable pa ern of trips (frequency, quality and
directness of bus, walk and cycle links to key destinations). It jumps quickly from trip
rates to junction modelling.
The North West Barry site’s location and arduous uphill topology prohibit any chance of
serious uptake of Active Travel commuting (on foot or by bicycle) from the nearest
commuter hub train station.
PPW and TAN 18 expect a sequential approach: location and accessibility first, then
network impacts—especially for greenfield housing that risks locking in car-based
patterns. The site patently fails in this regard.
6. Impact on Air Quality and noise levels due to traffic conges on
North West Barry Transport Assessment – Modelling Addendum (May 2025) — there are zero
references to:
 Air quality
 Air pollution
 NO₂ / nitrogen dioxide
 PM₂.₅ / PM₁₀
 AQMA / Air Quality Management Area
 Environmental impacts of traffic
 Health impacts of emissions
 Noise impact of traffic
 Air quality assessment requirements
There is no sec on, no paragraph, and not even a passing men on of an air quality assessment
being undertaken or even considered anywhere in the document provided.
Why this absence matters (policy context)
This omission is highly significant because:
i) PPW (Planning Policy Wales) requires air quality to be assessed, and impacts considered, as
part of the strategic traffic assessment process:
“For specific proposals, particularly those genera ng significant traffic, AQA must be included as
part of the transport assessment to assess impacts on, and in conjunction with, the surrounding
transport network”
Even if AQA’s have previously been undertaken as part of the local council’s statutory activity,
the lack of inclusion of any AQA data in the report is a glaring failure of the provided RLDP STA
data to comply with PPW requirements.
ii) TAN 18 (Transport) explicitly links traffic growth to air quality impacts
Especially at congested junctions — and Weycock Cross is repeatedly described as congested or
over capacity.
iii) Future Wales and the Wales Transport Strategy priori se reducing emissions
Any development genera ng additional car trips must demonstrate how it avoids worsening air
quality.
iv) The site is adjacent to a major arterial route (A4226) with peak-hour conges on
Congested, slow-moving traffic is the worst-case scenario for NO₂ and PM emissions.
v) The Dra Transport Assessment repeatedly proposes capacity-increasing measures
But never evaluates whether these:
 Increase induced traffic
 Increase emissions and pollution
 Increase noise and disturbance
 Affect local receptors (homes, school routes, pedestrians, cyclists)
7. Conclusions:
For the reasons outlined above, I believe it is clear that the not only is the North West Barry
KS1 site unsuitable for inclusion in the RLDP based on sustainable travel criteria alone, but
also the RLDP supporting evidence in the form of this 3rd party document does not meet the
expected standards required by PPW.