Policy aims - Transport Policy and Planning in Great Britain - page 187

Box 11.4 PSA targets relating to road traffic congestion
PSA1 [Applicable to the strategic highway network managed by the Highways
Agency]
For the purposes of this target the indicator is based on the whole of the motorway
and trunk road network, broken down into 100 or so 'routes', each averaging some
forty miles in length. The traffic speed on each of these routes is measured on a
series of links in both directions for 15-minute periods between 06.00 and 20.00. The
indicator is the average delay experienced in the worst 10% of situations (defined
by route, direction and time period). Delay is expressed as minutes per vehicle per
10 miles as compared with the 'reference speed', i.e. the speed at which motorists
could expect to travel in free-flow conditions. The target will be considered met if the
average delay in 2007/08 is less than that in the baseline period (2004/05). Because
the delay is expressed per vehicle an improvement will have to more than offset the
effects of likely increases in traffic volume.
PSA4 [Applicable to the networks managed by local authorities in the ten
largest urban areas in England, viz London and the six metropolitan areas (see
Fig 10.2) plus Nottingham, Leicester and Bristol]
For the purposes of this target the indicator is based on only a small proportion of
main roads within each area - in this case the routes are typically 2-5 miles in length.
Unlike the indicator for the strategic network, conditions are only measured during
the 'morning peak period' and may be in one (peak) direction only. Measurements
are of the average journey time per person (minutes per mile) and therefore require
separate observations of the number and speed of buses and other vehicles and of
their average occupancy.
The targets for each area have been developed as part of the LTP2 process and
explicitly incorporate the expected increase in local travel to 2010/11. The target
increase in average journey time during this period (on a nominal 2005 base) ranges
from 0% in Greater Manchester to 14% in Bristol. The national target is an average of
these area figures weighted according to their total traffic flow on all major roads. The
national target will be deemed to have been met if by 2010/11 an average increase in
travel of 4.4% has been accommodated in these areas with an increase of not more
than 3.6% in person journey times per mile.