This short presentation provides a summary of recent initial work undertaken by TRICS on trip generation comparisons between the UK and Ireland. 1
Before going through this initial, exploratory comparison exercise, I shall just update you on the status of TRICS in Ireland. The first contact between TRICS and the Irish transport planning/development control community took place in Dublin in 1999, when the TRICS Consortium visited Ireland to introduce the system to local authorities and consultants. This was a very helpful event, and led to the first Irish member organisations of TRICS in 2000. An annual data collection programme in Ireland was set up, which continues to this day across 6 regions, and at this point in time there are around 40 member organisations in both the Irish Republic and Northern Ireland. 2
There are 17 regions within the TRICS database, and 6 of these cover Ireland. These are Greater Dublin, Munster, Leinster, Connaught, Ulster (Republic of Ireland) and Ulster (Northern Ireland). It should be noted that TRICS data had been collected in Ireland prior to 2000, but it was only from 2000 onwards that a targeted programme in the Republic of Ireland commenced. 3
Currently, there are 391 days of TRICS survey data in the database, as at June 2012. Although the largest land use category is Residential, you can see from the information on this slide that surveys have taken place across all of the 16 main land use categories, and if you look at the bar chart you can see that TRICS has been covering each of the 6 Irish regions over time. In fact, every year some surveys will take place at each of the regions. 4
So, moving on to the initial trip rate comparison exercise. The aim of this exercise was for the TRICS Consortium to evaluate the data currently in the database and see if there is sufficient data available to compare UK and Ireland trip generation. The current version of TRICS was used for this exercise, and initially TRICS looked at 12 land use categories. The analysis consisted of a typical survey period (say 0700-1900 for sites such as residential, employment, etc), and also compared time periods of peak activity. For the first part of the analysis, surveys were not split by location type, although there was considered to be sufficient Residential data for there to be an additional subsequent analysis of this nature. 5
TRICS selected the land uses for this analysis based on categories where most comparative data was available. The categories consisted of the following: Office, Business Park, Houses Privately Owned, Flats Privately Owned, Mixed Private Housing, Primary School, Secondary School, Hotel, Private 18-Hole Golf Course, Civic Amenity Site, PFS with Retail, and Car Show Room. Unfortunately it would turn out that there was insufficient Irish data for most of these categories for their to be any reliable, robust comparisons, although there was one particular exception to this, as we shall see. 6
To run through the technical method used to ascertain the UK and Ireland trip rates, I can provide information on the selection criteria used. The analysis was based on the Total Vehicles count, using the main trip rate calculation parameter in the case of each land use category (for example Number of Dwellings for the Residential sub-categories). When filtering sites in TRICS, the default minimum and maximum trip rate parameter values were accepted (in order for there to be a reasonable sample of surveys), the minimum survey date cut off was set to 01/01/2000, only manual classified counts were included (so any ATC counts were removed), and only weekday surveys were selected (apart from the Golf and Civic Amenity categories which used weekend data). 7
What TRICS found, was that there was a strong similarity in trip generation between UK and Ireland Residential sites. There were three Residential land use categories tested, and one of these was considered to have sufficient data available. The 03/A (Houses Privately Owned) category indicated a robust correlation between UK and Ireland data. Unfortunately, as mentioned before there was insufficient Irish data in the other categories, once filtering had taken place, to come to any robust conclusions. However, there were encouraging signs that a more robust analysis of the other land uses could take place in time, if there could be a specifically targeted programme of surveys by land use category in Ireland. This is something that the TRICS Consortium may consider for next year s programme. 8
We can however focus on the one area where we did have enough data for a robust comparison, most significantly in the 03/A (Houses Privately Owned) sub-category. In this category, we had a good sample of 67 UK survey days and 29 surveys in Ireland. Looking at the results, the top table shows very similar trip rates of 5.199 per dwelling for 0700-1900 in the UK, and 5.339 per dwelling in Ireland, a difference of only 2.69%. This is very encouraging, and indicates with a good degree of reliability that data throughout the database in the 03/A land use can in principle apply to both the UK and Ireland. The lower table shows the 1700-1800 peak period, and again there is a close similarity between the UK and Ireland data, the trip rate varying by only 1.48%. 9
The size of the data sample for the 03/A land use category allowed TRICS to undertake a second analysis, this time splitting the survey days by Location Type. As you can see in the table shown here, the data was split by Edge of Town, Suburban Area, and Edge of Town Centre categories, although there ended up being insufficient data available for the Edge of Town Centre category to show any conclusive results. It would certainly be a good idea to target further surveys at this location type, both in the UK and Ireland. So we can only really look at the Edge of Town and Suburban Area categories. The table shows, again, that trip generation in the UK and Ireland is very similar, even when we consider the relatively low Irish data samples of 9 and 14 surveys respectively. The biggest percentage variation in the table is only 13.03%, when comparing Edge of Town trip rates covering the 1600-1900 period (the trip rates shown are 1.650 for the UK and 1.865 for Ireland, considered to be very similar when you take into account natural fluctuations in datasets), with the 13% being well within acceptable error margins. Again, this is encouraging for the use of TRICS in Ireland. 10
We can look at the Edge of Town trip generation profiles for the UK and Ireland in this slide. As you can see, there are similarities in the profiles, with the typical peak periods taking place during 0800-0900 and 1700-1800 (the graphs represent arrivals + departures). It would appear that similar patterns of activity take place at residential sites in the UK when compared to Ireland. 11
Similarly, we can see the profile for the Suburban Area location type. Again, the profile is very similar between the UK and Ireland. Note the 0800-0900 peak which is almost identical. 12
So, to conclude and offer some next steps in this work. This initial exploratory exercise has shown that there are strong similarities between UK and Ireland trip generation for the 03/A (Houses Privately Owned) land use category. There is clear evidence that trip generation and trip profiles are similar, and that the general TRICS database can be applicable to Irish sites for this land use. However, it is clear that there is a shortage of Irish data covering other land use categories that have made findings in these area inconclusive. A targeted programme of surveys in 2013 (particularly in Ireland) would allow further analyses to take place, and possibly a research document that identifies correlations across a variety of land use types. 13