Time Constraints: The Cost of Sustainability - Sustainable Urban Logistics: Concepts, Methods and Information Systems - page 166

step consists in identifying the (demand) market. The second step identifies the
time windows and vehicle restrictions that retailers and shopkeepers have to deal
with. The third step contains the optimization of the routes by means of Operations
Research techniques and calculates the fleet-seize and the individual truck per-
formances. The last step is calculating the total cost referred back to the individual
load units.
Thus, Groothedde et al. ( 2003 ) calculated that the delivery of a roll cage for a
(large) supermarket in an inner urban area with restrictions (i.e. access time
windows and weight or length restrictions) on average costs 7.50 Euros, while
such a provision in a village costs on average 5.40 Euros. Based on these calcu-
lations, the additional logistical costs for the Dutch supermarket sector as a result
of access time windows and vehicle restrictions matched exactly 100 million
Euros. Also additional costs were estimated for the entire Dutch retail trade, which
amounted for 425 million Euros. All the data used in the analysis was obtained
from 5000 stores representative in 9 different branches of the Dutch retail sector.
van Rooijen et al. ( 2007 ) examined the Dutch cities and simulate specific time
windows to complement the previous study a number of policy options. Five
practical policy options were investigated:
• abolition of time windows in towns with less than 50,000 inhabitants;
• regional coordination of time windows;
• a uniform window from 7:00 to 9:00 h in all municipalities;
• a uniform window of 7:00 to 1:00 p.m. h;
• a uniform window of 7:00 to 7:00 p.m. h.
The effect of these access time window regulations were calculated for various
retail chains in 4 sectors: supermarkets, department stores, drug stores and elec-
tronics shops. In the reference run the time window lasted on average 4.7 h a day
for a municipality. The results showed that a uniform extension of time windows
gives the best results. An average extension of the time windows of about 1 h in all
municipalities gave more than 2 % reduction in vehicle kilometers and 6 % fleet
reduction. These savings were roughly the same as if the time windows in the
smaller municipalities would disappear. In case all municipalities had no time
window regulations the savings in vehicle kilometers went up to 4 %, while the
savings on fleet-seize grew to a substantial level of 23 %. The benefits of night
distribution were also examined and showed a saving of almost 17 % of the total
fleet. Surprisingly the savings on the number of vehicle kilometers by night
delivery remained zero. The conclusion was that a uniform extension of time
windows gave the best results (van Rooijen et al. 2007 ).
Finally, Quak ( 2008 ) examined in detail the effectiveness of broadening time
windows. He compared the scenario of current access time windows in the
Netherlands, fees and other access restrictions, with a softer regulation scenario
with longer access time windows, between 7 and 11 h. The analysis concluded that
the current scenario leads to a cost increase between 12 % and 38 %, whereas the
modified situation, applying time windows from 7:00 to 11:00 a.m., lead to a total