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83 Land Use A Land Use B for example, for Mockingbird Station, 63% of the trips from 75 35 office goes to internal restaurants, while at Atlantic Station 50 25 and Legacy Town Center, the corresponding trips amounted to 5% and 8%, respectively. At Mockingbird Station there 35 was a specialty coffee restaurant less than 200 ft from the 25 office building. No other restaurants were open in the devel- Figure 19. Example of unconstrained demand and opment in the morning. The office building had no internal balancing of internal trip interchange. coffee or snack shop. There was a steady stream of people going between the office building and that restaurant during the morning peak period. The other two developments each Internal capture percentages in the previous tables are sim- had similar restaurants; however, they had roughly 3 to 5 times ilar for some land use pairs but not for others. One reason for the office space, they were several blocks away, and Atlantic this is the balance between land uses. If two land uses are bal- Station's office building had a coffee stand in its lobby dur- anced for the purpose of trip generation interaction, Land Use A would want to send as many people to Land Use B as ing the morning peak. It is no surprise that the Mockingbird Land Use B would want to receive from Land Use A. Station capture rate is much higher than that for the other However, consider a case where Land Use A wants to send two developments. 75 trips to Land Use B, but Land Use B only wants to receive Table 98 contains a comparison of land use development 35 trips from Land Use A (see Figure 19). Land Use B will unit ratios and internal capture rates for land use pairs in receive all the Land Use A trips it wants: it can be considered Tables 94 through 97 for which one internal capture percent- to be unconstrained. There are more than enough Land Use age is much higher than the other two. Table 98 displays rel- A trips to satisfy Land Use B demand; however, Land Use A ative constraints on trips in the form of the ratio of develop- demand to send trips to Land Use B is constrained because ment units, which is somewhat of a surrogate for total trips Land Use B will accept only half of the trips Land Use A wants made. For exiting trips, the higher the ratio of origin devel- to send. Examining the opposite direction, Land Use B wants opment units to development units, the constraint is greater to send 25 trips to Land Use A, and Land Use A wants to (i.e., the fewer the development units at the destination end). receive 50 trips from Land Use B. Because all of the Land Use For entering trips, the lower the ratio, the constraint is greater B trips can be accepted by Land Use A, Land Use B is uncon- (i.e., the fewer the development units) at the origin end of the strained in that direction, but Land Use A is constrained. trip. Hence, a high internal capture percentage for exiting trips When internal trips are constrained, they cannot occur, could be expected where there is a low development unit ratio and the travel demand must be satisfied externally. Figure 20 and proximity. For example, for P.M. peak-period trips from shows what happens in these two examples. Land Use A wants retail to residential at Legacy Town Center, 196,000 sq ft of to send 75 trips to Land Use B. Only 35 of those trips can retail were feeding trips to 1,360 units of residential (144 sq ft go to Land Use B internal to the development, so the other of retail per dwelling unit) at an average distance of 1,240 ft, 40 trips have to seek Land Use B externally. This is based on resulting in 26% internal trip capture. On the other hand, for the assumption that people make trips for a purpose (e.g., eat the same interchange, Country Isles had 109,000 sq ft of retail lunch), and if that purpose cannot be satisfied internally feeding 368 residential units (296 sq ft of retail per residential where it is most convenient, the trip maker will have to find unit) at an average distance of 1,525 ft, resulting in 4% inter- someplace to eat externally. nal capture. The origin end trips were more constrained at the Therefore, returning to Table 94, the (major) differences destination end at Country Isles (about half as many units between the internal trip capture percentages that appear in receiving trips). In addition, the separation was greater, further this table are attributable in many cases to the balance, lack of constraining trips from retail to residential. constraints, or other factors that exist for some zone pairs-- Such is the case for most of the examples shown in Table 98. Except for P.M. peak-period entering trips, constraints imposed by development unit ratios and greater proximity distances Land Use A Land Use B result in the lower internal capture percentages. 75 35 50 25 Conclusions 35 25 0 As Table 98 shows, lower ratios and higher proximity tend 25 40 0 to result in higher capture rates. The highest percentages of Figure 20. Continuation of Figure 19 example showing internal capture are associated with lesser levels of con- external trips resulting from internal constraints. straint and higher proximity. Only additional data will confirm
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84 Table 98. Comparison of internal capture by development unit ratios and proximities for selected land use pairs. Land Use Development Units2 Internal Proximity Site1 Ratio3 Capture Comments Origin Destination Origin Destination (ft)4 (%) Morning Peak-Period Exiting Trips (from Table 94) Proximity similar to LTC; most AS 551 1.6 344 1,000 5% constrained at destination. Proximity similar to AS; slightly Office Restaurant LTC 311 5.1 61 1,200 8% more constrained than MS. Closest proximity; close to least MS 115 1.5 77 200 63% constrained at destination. Farthest separation; most AS 798 1.6 499 2,300 0% constrained at destination. Residen- Moderate proximity; somewhat Restaurant LTC 1,360 5.1 267 1,470 7% constrained at destination. tial Closest proximity; least constrained MS 191 1.5 127 100 20% at destination. Afternoon Peak-Period Exiting Trips (from Table 95) About middle for both proximity AS 551 435 1.29 660 6% and constraint at destination. Third longest separation; third most LTC 311 196 1.59 975 0% constrained at destination. Close to least constrained at MS 115 156 0.74 320 9% destination; closest proximity. Office Retail Second longest separation; second BDM 316 151 2.09 1,125 0% most constrained at destination. Least constrained at destination; CI 75 109 0.69 775 9% third closest proximity. Most constrained at destination; VC 315 121 2.60 1,600 6% longest separation. Second most constrained at AS 435 798 0.55 2,280 13% destination; longest separation. Least constrained at destination; LTC 196 1,360 0.14 1,240 26% third longest proximity. Most constrained at destination; MS 156 191 0.82 170 7% closest proximity. Retail Residential Least constrained at destination; BDM 151 1,144 0.13 825 3% second longest separation. CI 109 368 0.30 1,525 4% Moderate constraint and proximity. Most constrained at destination; VC 121 317 0.38 900 7% moderate proximity. Third least constrained at AS 65 798 .081 2,360 3% destination; longest separation. Third least constrained at LTC 69 1,360 .051 1,325 18% destination; third longest separation. Most constrained at destination; MS 29 191 .152 200 3% closest proximity. Restau- Residential Least constrained at destination; rant BDM 34 1,144 .030 1,100 6% fourth longest separation. Second longest separation; second CI 21 368 .057 1,600 -- most constrained at destination. Second most constrained at VC 42 317 .132 600 4% destination; second closest. proximity. Morning Peak-Period Entering Trips (from Table 96)--no instances of one internal capture percentage much higher than at least two others Afternoon Peak-Period Entering Trips (from Table 97)--no instances of one internal capture percentage much higher than at least two others Third least constrained at origin; AS 435 551 0.79 895 31% second closest proximity. Third most constrained at origin; LTC 196 311 0.63 975 6% third longest separation. Close to least constrained at origin; MS 156 115 1.36 150 5% closest proximity. Retail Office Second most constrained at origin; BDM 151 316 0.48 1,125 0% second longest separation. CI 109 75 1.45 775 2% Least constrained at origin. Most constrained at origin; longest VC 121 315 0.38 1,600 0% separation. Second most constrained at origin; AS 798 551 1.45 3,100 0% farthest separated. Close to least constrained at origin, LTC 1,360 311 4.37 900 57% second closest proximity. Third most constrained at origin; Residen- MS 191 115 1.66 225 2% closest proximity. Office Third least constrained at origin; tial BDM 1,144 316 3.62 2,000 0% second farthest separated. Least constrained at origin; third CI 368 75 4.91 1,000 0% closest proximity. Most constrained at origin; third VC 317 315 1.01 1,750 0% farthest separated.
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85 Table 98. (Continued). Land Use Development Units2 Internal 1 Proximity Site Ratio3 Capture Comments Origin Destination Origin Destination (ft)4 (%) Most constrained at origin; second AS 65 435 0.15 430 28% closest proximity. LTC 69 196 0.35 500 17% Least constrained at origin. Second most constrained at origin; MS 29 156 0.19 300 50% closest proximity. Restau- Retail Third most constrained at origin; rant BDM 34 151 0.23 800 1% third longest proximity. Second most constrained at origin; CI 21 109 0.19 1,200 0% second longest separation. Least constrained at origin; second VC 42 121 0.35 1,100 1% longest separation. 1 AS = Atlantic Station; LTC = Legacy Town Center; MS = Mockingbird Station; BDM = Boca del Mar; CI = Country Isles; VC = Village Commons. 2 All development units are in gross sq ft except residential, which is in dwelling units; development units shown for restaurant during morning peak are for those restaurants that were open. 3 Origin development units/destination development units. For exiting trips, this constraint at destination end is represented by highest ratio. For entering trips, highest constraint at origin is represented by lowest ratio. 4 Separation between interaction land uses based on average weighted by trips (rounded to closest 100 ft). whether other similarly unconstrained and high proximity want to go there, only eight can be seated. The restaurant seat- examples will demonstrate similar internal capture findings. ing constrains the interaction between the two land uses. Where the highest internal capture percentage accompanies Now compare that development to the next similar devel- both the least constrained and highest proximity, the reported opment down the street where 25 office employees want to internal capture percentage is probably close to the maximum go to a restaurant with 16 seats. At that location, as many as the researchers would expect to find. These percentages could 16 employees can go to that restaurant, so even though the be considered unconstrained internal capture percentages. restaurant is again the constraint, the interaction is greater. However, where the highest internal capture percentage for a For the third example, consider that 25 office employees can land use pair and period is associated with either a moderately go to an onsite restaurant with 40 seats. In this example, all high constraint and/or a proximity significantly farther than 25 employees can be seated. In fact, more could be seated. In the minimum, the researchers expect that future surveys could this example, the office building is the constraint. find higher internal capture percentages. For now, the highest Hence, with differing balances of the land uses making up internal capture percentages reported in this report for each the six surveyed developments, it is understandable that the land use pair and time period should be considered the docu- internal trip capture percentages vary among them. Some mented unconstrained internal capture percentages and should of the differences may be explained by the travel distances be used as unconstrained values. between trip origins and destinations--that is, proximity. In general, the three developments surveyed for this project Proximity is addressed in a later section. In addition, there are more compact, are better connected, and have more com- are other factors not quantified in this research that may also ponent land uses than do the three Florida developments. affect internal capture such as attractiveness of specific busi- Additionally, the three developments surveyed for this proj- nesses, demographics of trip-makers, and alternative oppor- ect generally have higher internal capture percentages. This tunities for similar destinations at nearby developments (i.e., confirms--at least based on the available data--that internal competing opportunities). While these may influence inter- capture can be increased through the use of more interacting nal trip capture, they may not be known at the time a devel- land uses, better connectivity, and/or more compactness. Com- opment is proposed, so it would be difficult to project those pactness or proximity is addressed later in this section. characteristics even if a method of projection was available. Unconstrained internal capture between individual land Tables 99 through 102 show the highest values from uses ranges from a low of none found to highs of over 60%. The Tables 94 through 97. The values of Tables 99 through 102 comparisons also show a wide range of internal capture rates show how much internal capture was achieved by the best between land use pairs. This results from a number of factors, balances between interacting land uses. In terms of the office/ the most important and projectable of which (at time of zon- restaurant example described previously, the values of Tables 99 ing) is the balance between land uses within a development. through 102 demonstrated the most unconstrained individ- To demonstrate this phenomenon, consider an office building ual conditions observed at the six developments. with 20 employees who want to go out for lunch at an onsite Although it is very possible that MXDs with other balances restaurant. The restaurant has eight seats. If all employees of development may experience even higher percentages, at
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86 Table 99. Proposed unconstrained values for percent distribution of internal trip destinations for exiting trips--A.M. peak period. Origin Land Destination Land Use1 Use Office Retail Restaurant Residential Cinema Hotel Office N/A 28% 63% 1% N/A 0% Retail 29% N/A 13% 14% N/A 0% Restaurant 31% 14% N/A 4% N/A 3% Residential 2% 1% 20% N/A N/A 0% Cinema N/A N/A N/A N/A N/A N/A Hotel 75% 14% 9% 0% N/A N/A 1 Corresponds to ITE Trip Generation Handbook Table 7.1; N/A signifies no data or interchanges within same land use categories that are accounted for within ITE trip generation rates. Table 100. Proposed unconstrained values for percent distribution of internal trip destinations for exiting trips--P.M. peak period. Origin Land Destination Land Use1 Use Office Retail Restaurant Residential Cinema Hotel Office N/A 20% 4% 2% 0% 0% Retail 2% N/A 29% 26% 4% 5% Restaurant 3% 41% N/A 18% 8% 7% Residential 4% 42% 21% N/A 0% 3% Cinema 2% 21% 31% 8% N/A 2% Hotel 0% 16% 68% 2% 0% N/A 1 Corresponds to ITE Trip Generation Handbook Table 7.1; N/A signifies no data or interchanges within same land use categories that are accounted for within ITE trip generation rates. Table 101. Proposed unconstrained values for percent distribution of internal trip origins for entering trips--A.M. peak period. Origin Land Destination Land Use1 Use Office Retail Restaurant Residential Cinema Hotel Office N/A 32% 23% 0% N/A 0% Retail 4% N/A 50% 2% N/A 0% Restaurant 14% 8% N/A 5% N/A 4% Residential 3% 17% 20% N/A N/A 0% Cinema N/A N/A N/A N/A N/A N/A Hotel 3% 4% 6% 0% N/A N/A 1 Corresponds to ITE Trip Generation Handbook Table 7.2; N/A signifies no data or interchanges within same land use categories that are accounted for within ITE trip generation rates. Table 102. Proposed unconstrained values for percent distribution of internal trip origins for entering trips--P.M. peak period. Origin Land Destination Land Use1 Use Office Retail Restaurant Residential Cinema Hotel Office N/A 8% 2% 4% 1% 0% Retail 31% N/A 29% 46% 26% 17% Restaurant 30% 50% N/A 16% 32% 71% Residential 57% 10% 14% N/A 0% 12% Cinema 6% 4% 3% 4% N/A 1% Hotel 0% 2% 5% 0% 0% N/A 1 Corresponds to ITE Trip Generation Handbook Table 7.2; N/A signifies no data or interchanges within same land use categories that are accounted for within ITE trip generation rates.