The study updated and extended earlier research undertaken in the UK in 1998.  It examined congestion impacts across nine sectors and enquired about company reactions to the significant deterioration in road traffic conditions in the UK over the previous decade.  

The research began with a review of relevant literature published since 1998.  This indicated that relatively little new work had been done on this topic in the intervening years.  One of the most fertile sources of new data was the UK government’s transport KPI programme.   Since 2002, it had collected data on the duration and causes of delays to around 55,000 road freight journeys across seven sectors.  This consolidated data set has been analysed for the first time in this study. 

The study also explored the relationship between traffic volumes along a sample of routes and the variability of transit times.  It used a newly-developed vehicle routing software tool to analyse link- and time-specific traffic flow data obtained for the UK trunk road network from the Highways Agency.  This modeling found very close correlations between the earliest and latest arrival times for freight journeys and the distance travelled, confirming the view expressed by logistics managers that most congestion is regular and predictable. 

In the course of the project a total of 37 managers were interviewed in 28 companies or divisions of companies.  Five visits were made to DCs, two of which were included in the 1998 survey.  Detailed enquiries were made about the impact of congestion on the logistics operations, the relationship between congestion and other sources of unreliability and any measures companies were taking to mitigate the effects of congestion.   Very few of the companies consulted were able to provide hard statistical data on the operational and financial impacts.  Most of the data collected was therefore qualitative. 

Analysis of the interview data revealed wide variations in the relative impact of congestion both within and between sectors.   There was little evidence of it causing companies to restructure their logistics systems.  Nor, in most cases, was it causing companies to run more vehicles, increase tractor-trailer ratios, carry more inventory or modify internal warehouse design and capacity.   As most congestion is fairly regular and as congestion levels have increased gradually, companies had learned to ‘work around it’, altering schedules, building in extra slack, making internal processes more flexible and, in some cases, upgrading their IT systems with telematics and routing software.  Some companies, however, have high exposure to congestion as a consequence of their geography, product type, scheduling constraints and customer requirements.   Congestion was clearly impacting more seriously on the cost and quality of their logistics operations. 

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The results were summarised in a journal paper: 

McKinnon, A.C., J.B.Edwards, M.I.Piecyk and A.Palmer (2009) ‘Traffic Congestion, Reliability and Logistical Performance: A Multi-Sectoral Assessment’  International Journal of Logistics: Research and Applications, 12 (5), 331-345.

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