TOPIC 33 DISCREPANCIES REPORT COMMENT

 Top of page 3 provides “79% of licensed HGVs are commercial”. 

Comment: Table VEH0102 provides (470.1m) HGVs and Table VEH 0103 provides (389.9m) goods veh.  Hence Goods vehicles as a percent of the whole are (389.9/470.1) = 83%, not 79%.  Perhaps they worked it out incorrectly thus [(470/389.9)-1] = 79%, or have a different data source.

 Page 2, Geographical coverage.  It says, “Foreign HGVs account for 945m vkms of total traffic (3.6% of traffic of GB roads)”.  There are also 90m vkms of NI lorries

Comment;  It should  say 3.6% of HGV traffic on GB roads.

 Page 3, 5-axle artics: It says, “The RT estimate of 5-axle articulated HGV traffic is 4 billion vkms higher than the CSRGT estimate. Reasons for this difference include the treatment of HGVs with trailers as articulated by the RT estimates ….”

Comment: That cannot be correct.  The CSRGT subdivides by trailer and  type.  Our subsequent combinations match RT classification.  RT provided 5.6b veh Km.  The CSRGT combination provided 1.7b – see table below. 

Comment There is heavy use of the word “may”.  Is it really so that enumerators count 6-axle vehicles with one raised as though with 5-axles or is it only the Acts that do that? 

Further, we see raised s on all HGVs except 3-axle artics and two  rigids (for which raised s are an impossibility), not just on 6-axle artics.

Page 9, use of HGV estimates:  Text contains no advice as to how to adjust the published data.  Some of the  links overleaf - page 10 appear inert.(nos, 2, 4,5 and 6)

Annex B provides differences between the RT and CSRGT.  The percentages are with respect to the RT but the table does not make that clear.  The same should be published with respect to the CSRGT for which the percentages are very much, if not catastrophically, larger.

Appendix F

No attempt is made to correct the estimates of tonne-km or tonnes lifted.

TSGB 0401 provides data which appears to compare road freight with rail, water and pipe line.  Whether or not there is survey error in the road freight data, it excludes freight in foreign, and NI lorries.

We say best estimates of road freight on UK roads are to be had by calculating the average loads by vehicle type from the CSRTG data and applying those to best estimates of Goods Vehicle vkms from the RT survey.

In that context we:

1. Set the non-goods vehicle HGVs to 17% of the total, see the first comment in this note, and allocate of them to the 2-axle class of HGV. We then assume that they each travel one quarter of the distance of an equivalent 2-axle goods vehicle.  On that basis we reduce the 2-axle HGV vkms by (25bn x 0.17/4) = 1,100m vkms
2. Adjusted the numbers in the classes by assuming 35% of 6-axle artics had one axle raised thereby being incorrectly counted as 5-axle artics.  Similarly we assumed 10% of 5-axle artics, 5% of 4-axle rigids and 5% of 3-axle  rigids had an axle raised.  (4-axle artics were combined with 3-axle artics.  Consequently no correction was applied there).  Those adjustments do not affect the total number of vkms. Instead the adjustments alter the vkms in each class.

That procedure yields 176 billion tonne-km (excluding freight in light goods vehicles).  The original Freight Stats provide 139 bn Tonne-km with no Light Goods, RFS0107, and 151 bn with Light Goods, TSGB 0401.  Hence the light goods element totals 12bn tonne-km   Adding that to the 176bn provides 188bn as the better number for road freight.  The 188bn is 25% above the value of 151bn cited in TSGB 0401.  As a sensitivity test we doubled the 1,100 vkms at (a) above.  The effect was to change the 25% cited in this paragraph to 24%.

 The following table provides comparative data: 

The comparison of Veh-km and the RT adjusted the CSRGT adjusted flows is fair particularly after noting that the RT value for 5-axle artics includes 1035 million vkms for foreign and NI lorries excluded from the CSRGT.

Further, the ratio of the RT total goods-veh flow of 23,835 to the original CSGRT value of 18,769 provides 1.27, showing that our adjustments to the numbers in each class had little or no effect on the estimates of tonne-km.