Practices for Permitting Superheavy Load Movements on Highway Pavements (2015)

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19 chapter three SURVEY RESULTS The web-based survey was circulated to state officials dealing with the permitting of heavy trucks and to state transportation engineers who assist the former with evaluating the impact of these vehicles on the pavement infrastructure. The distribu- tion list for the survey was developed by updating a contact list obtained from the Specialized Carriers and Rigging Asso- ciation. Additional work was carried out to expand and update the list by identifying the names and contact information of the department of transportation pavement engineers who conduct the analysis of the SHCV being considered for permitting. The survey was circulated by e-mail on January 15, 2014, and follow-up phone calls were made to encourage maximum par- ticipation. The survey ran until July 30, 2014, at which point it was closed and the data were analyzed. A total of 39 states and five Canadian provinces responded. The corresponding response rates were 78% and 50%, respectively. Eight of the responding states submitted two separate responses, one from a permits official and the other from an engineer performing the impact evaluation. This brought the total number of the responses analyzed to 52. A list of the responding states and provinces and the job titles of the officials who responded to the survey is shown in Appendix B. The raw survey question- naire responses are included in Appendix C. The following summarizes the survey questionnaire results and is divided into four parts: 1. Definition of SHCVs, 2. Pavement analysis details, 3. SHCV permit fees, and 4. Number of permits/type issued. DEFINITION OF SUPERHEAVY COMMERCIAL VEHICLES This section summarizes the survey results related to back- ground questions and the way SHCVs are defined and per- mitted in each jurisdiction. Several options were offered in defining SHCV vehicles; namely, the number of axles, GVW only, GVW and axle load regardless of axle spacing, and GVW and axle load as a function of axle spacing. Figure 4 shows the distribution of agency responses to this question. It sug- gests that 16 of the responding agencies (41%) define SHCV in terms of a maximum GVW alone. The distribution of these GVW limits is plotted in Figure 5. They vary widely from 120 to 500 kips, with the most frequent value being 200 kips. Five of the responding agencies (13%) reported that they define SHCV in terms of GVW and axle group limits regardless of axle spacing. The distribution of these GVW limits and the axle group load limits are listed in Table 9. The wide range of GVW and load limits is again evident; GVW limits range from 80 kips to 350 kips and tandem axle loads, for example, range from 34 kips to more than 60 kips. Another five of the respond- ing agencies (13%) define SHCV in terms of GVW and axle group limits as a function of axle spacing. The distribution of these GVW limits, the axle group load limits, and the cor- responding minimum axle spacings are listed in Table 10. In this case, GVWs vary from 100 to 254 kips, tandem load limits from 40 to 50 kips, whereas minimum tandem axle spacings vary from 6 to 12 feet. Interestingly, the remaining 13 of the responding agencies (33%) specified more complex definitions for SHCV under “other.” Several of these alterna- tive definitions are quoted here: • Class C Permits/Superloads . . . are for loads that exceed 120′ in length, 14′ in width, 16′ in height, and more than 250,000 lb GVW (any combination) or exceeding allow- able weights on restricted bridges. • Loads in excess of routine permit limits will be consid- ered according to the following regulations when air, rail, or water terminal points are not available: (A) All permit applications with dimensions or weights exceeding the routine limits of the preceding oversize and overweight permit rule (i.e., generally in excess of 16 feet wide, 16 feet tall, 150 feet long and/or over 160,000 lb GVW). • Exceeding 25 axles or the combination of wheel base/ number of axles and tabulated GVW values. • A vehicle that is considered “excessive overmass” when entered into our special permitting system and requires evaluation by the bridge engineer office of the Depart- ment of Transportation & Works. • Weight requires approval of the department’s bridge bureau. • Exceeding a certain GVW and/or exceeding a certain load by axle group as a function of axle spacing and/or exceeding the pre-approved weight threshold for its requested route. • Exceed axle group weights. Must have more than 4 tires per axle • We don’t use this (the SHCV) term. • We can permit very large loads over the axle load on a wide axle (over 8’ outside tire to outside tire), but can’t permit for more than 600 lb/in. tire load. • Exceeds a certain GVW and occupies two lanes.

20 Policies also vary in terms of the definition of a “non- divisible” load. Twenty-six of the 42 agencies that answered this question (62%) indicated that they do have a definition of what a non-divisible load is, while the remaining 16 (38%) do not. Of those that do have a definition, 11 (42%) described it in terms of the number of work days that would be required to break it down into smaller shipments (i.e., the remaining 15 indicated “other” without providing any specifics). Their responses are shown in Figure 6. Clearly, there are signifi- cant differences between jurisdictions as to the definition of a non-divisible load to be carried by a SHCV. The survey included additional questions as to whether hard axle load limits and unit tire loads (i.e., lb/in. of tire width) are set by legal statute. Of the 42 agencies that answered the first question, half said that they do limit axle loads by statute, and the other half that they do not. Of the 39 agencies that answered the second question, 39% (15) stated that they do limit unit tire widths by statute, while the remaining 61% (24) stated that they do not. PAVEMENT ANALYSIS DETAILS A total of 40 agencies replied to the question as to whether or not they perform a pavement impact analysis as part of evaluat- ing SHCV permit applications. Figure 7 shows the distribution of their responses. It suggests that only 22 of the 40 respond- ing agencies (55%) perform pavement analysis for permit- ting SHCVs. Of those, six always do (Delaware, Louisiana, Missouri, Mississippi, Tennessee, and Vermont) and 16 do so depending on the circumstances (Arizona, Colorado, Iowa, Illinois, Indiana, North Dakota, North Carolina, Oregon, Tennessee, Texas, Virginia, Washington State, Wisconsin, Wyo- ming, British Columbia, and Ontario), whereas the remaining 18 agencies (45%) never perform such analysis. Several of the agencies that answered “it depends” provided additional comments describing the circumstances under which they undertake pavement impact analysis prior to permitting SHCVs. Some of these comments are listed here verbatim: • Normally if the GVW is more than 500,000 lb or/and per axle load exceeds 30,000 lb. The analysis of the pavement is performed by the Pavement Division. I do the bridge analysis of all bridges on the proposed route if the GVW is 200,000 lb or more. • The Ministry has provisions in our O/O [oversize/ overweight] permit issuing policies allowing for pave- ment analysis under exceptional loadings; however, we have not resorted to this requirement in over 25 years. • Rare situation of exceeding 25 axles or exceeding tabu- lated values. • If the load is exceptionally heavy or if the pavement is breaking up we might. It is on a case-by-case basis. • Anything over 20,000 lb per axle. • If the GVW exceeds 270 kips the application is referred to pavement engineers for a standard review. “Detailed analysis” may be required if axle loadings exceed 27,000 lb per line or time of travel coincides with spring FIGURE 4 Vehicle characteristics used to define SHCVs. FIGURE 5 SHCV definition based on GVW only.

21 thaw, flooding, or other unusual weather that is likely to reduce road strength. • Our bridge analysis engineers involve the geo-technical branch for pavement considerations on requests that are unusually heavy or where there is some unknown factor on the requested route that would be of interest to the pavement engineers. • All loads are processed through the bridge analysis and, if they pass, then away they go. • There are cases of pavement studies undertaken for introduction of new vehicle configurations. • For the most part detailed analysis is not required. It is on a case-by-case basis. • The Pavement Section sets criteria for us to follow. Send all information to them if the GVW exceeds 800,000 lb or if load exceeds 500,000 lb and 6,000 lb per wheel load. • Answered by the pavement engineers: If axle weights exceed 29,000 lb. • Bridges are the limiting conditions; require axle and tire loads to be limited to reduce potential impacts to pavement. • We have performed pre- and post-pavement review for some loads exceeding 1,000,000 lb. • We require bridge analysis, but not specific pavement analysis. If it is determined necessary to require pave- ment analysis we have the authority to do so but I have not seen this required. • When travel is required on a highway that has been weight restricted additional pavement analysis is required. Evidently, the criteria used for deciding to perform a pave- ment analysis as part of the permitting process of superheavy vehicles are more complex than simply their classification as a SHCV by means of their GVW or axle weight and axle spacing. The type of pavement analysis performed varies as indi- cated by the 16 agencies that responded to this question (Figure 8). The majority of these jurisdictions use either their own in-house developed mechanistic-empirical pavement analysis approach or the mechanistic methods developed by industry; for example, the Asphalt Pavement Association (27) — no maximum weight specified. GVW Limit (kips) Load Limits by Axle Configuration (kips) Single Tandem Tridem Quad 150 24 48 60 60 80 28 34 56 — 350 26 — — — 250 30 60 60 60 125 28 50 60 — TABLE 9 DEFINITION OF SHCV USING GVW AND AXLE WEIGHT (FIVE JURISDICTIONS) — none specified. GVW Limit (kips) Axle Configuration Single Tandem Tridem Quad Max. Load (kips) Min. Spacing (ft) Max. Load (kips) Min. Spacing (ft) Max. Load (kips) Min. Spacing (ft) Max. Load (kips) Min. Spacing (ft) 140 22 — 40 6 48 12 60 15 171.96 24 — 50 10 >60 12 >60 — 254.3 24 12 46 12 60 12 >60 — 100 24 — 48 — 60 — 60 — 232 22 9 48 9 60 9 >60 — TABLE 10 DEFINITION OF SHCV USING GVW, AXLE WEIGHT, AND AXLE SPACING (FIVE JURISDICTIONS) FIGURE 6 Defining “non-divisible” loads in terms of the number of work days required to divide them.

22 and Portland Cement Association (28). These methods rely on structural analysis models, typically layered elastic analysis for flexible pavements, and finite element analysis for rigid pavements. They allow direct input of axle loads and com- pute their impact on performance through transfer fractions that translate stresses and strains to pavement damage (i.e., cracking rutting and so on). Several agencies indicated that they use the 1993 AASHTO Guide for the Design of Pave- ment Structures (21) and characterize the traffic in terms of ESALs, while one agency takes a hybrid approach using the 1993 AASHTO Guide for the Design of Pavement Structures, with load equivalency factors computed mechanistically (i.e., ratios of pavement damage computed as a function of strain ratios). None of the responding agencies indicated using the Mechanistic-Empirical Pavement Design Guide (8) for evalu- ating the impact of SHCVs on pavements. Additional details on the pavement analysis performed for permitting SHCVs are shown in Figures 9 and 10. Figure 9 shows that the majority of the 15 jurisdictions that responded to this question perform such analysis using representative thickness and layer/subgrade moduli for the entire route, while few consider seasonal variations in layer properties. Figure 10 indicates that most agencies analyze the full length of the vehicle (i.e., all the axles), about half consider only one wheel path and the actual number of tires in the wheel path and their tire inflation pressure, whereas only approximately 25% of them consider the vehicle speed. Figure 11 suggests that only four of the 15 responding agen- cies (27%) consider the stability of the pavement subgrade. Of those four, two specified the type of subgrade analysis conducted, one indicated that it uses a Mohr–Coulomb type of analysis, and the fourth that they use a slope-stability numerical method for the analysis. Figure 12 suggests that where there is a risk for excessive pavement/subgrade damage from a proposed SHCV, agen- FIGURE 7 Distribution of states/provinces responses to whether they carry pavement analysis as part of SHCV permitting. FIGURE 8 Type of pavement analysis performed.

23 cies are most likely to either request a different axle con- figuration from the shipper or would propose an alternative route with stronger pavements. A few agencies would either request that the shipment be divided up and some that protec- tive measures are taken to reduce the risk of damage to pave- ments and utilities (e.g., steel plates over water and sewer lines). Several jurisdictions replied “other” to this question. Some of their comments are listed here: • The moving company is requested to post a bond to cover potential pavement damage. • Has not occurred to date. • Shipper is requested to conduct FWD [falling weight deflectometer] testing before and after to detect any dam- ages to the pavement/subgrade. • We provide a number of suggestions to the shipper and we allow them to choose what is appropriate among these suggestions and then resubmit for a second round of reviews. • If nothing can be done by the carrier to better spread the load, deflection tests and condition evaluations are conducted. • Action is guided by a flow chart provided (see Figure 2 in chapter two). SUPERHEAVY COMMERCIAL VEHICLE PERMIT FEES Survey questions on the way the actual SHCV permit fees are calculated revealed substantially different methodologies between jurisdictions. Figure 13 shows that for establishing their SHCV permit fees, 15 of the 46 responding agencies (33%) use a GVW-distance traveled approach (Alabama, Florida, Illinois, Ohio, Missouri, Montana, North Dakota, Tennessee, Utah, Vermont, Washington State, West Virginia, Wyoming, British Columbia, and Ontario), two use a pavement damage- distance traveled approach (Arizona and Oregon), and two use a number of axles-distance traveled approaches (Idaho and New Jersey). Furthermore, 19 of the 46 responding agen- cies (41%) selected “other” in answering this question. Some of the explanations provided in selecting “other” are shown here: • Carrier pays for all incurred damages. • There is a fee for a bridge analysis when the load exceeds #250,000 pounds or exceeds the allowable weight on a restricted bridge; $125.00 per 50-mile increment of pro- posed route. • The permit for SHCVs is $110.00 plus we charge the company requesting the move for the detailed bridge analysis, which is an hourly rate for the engineer. FIGURE 9 Structural details of the pavement analysis. FIGURE 10 Load analysis details. FIGURE 11 Pavement subgrade stability analysis details.

24 • Flat fee of $10 is charged for all permit loads. • Flat fee $10 for a single-trip permit. • Fees are calculated on the basis of weight. • Basic fee plus weight fee. • Fees are regulated under the Motor Vehicle Act (Regu- lation 89-65). They are based on type of permit, vehicle configuration, GVW, and duration. • A single-trip permit for an oversize/overweight permit is issued per each load. If a load exceeds the weight per number of axles, an additional overweight fee is charged at a rate of two cents per ton-mile for the excess weight. • Standard fee of $250 per trip. • There is a vehicle supervision fee and a permit fee. The vehicle supervision fee is based on whether the load crosses bridges or not. The permit fee is a flat fee for the permit and additional fee for the weight. • A flat fee is charged for all permits, superload or routine issue. These are established by regulation. • Fees are both codified and regulatory. Please review VA Code: 46.2-652.1 to see pavement damage-related fees • GVW - 80,000 lb/2000 = Ton Mile × $.50 × Actual Mile- age + $10.00 Admin Fee + Structural Evaluation Fee = Permit Fee. • Determined by vehicle size + ton/mile fee. FIGURE 13 Methods used for calculating SHCV permit fees. FIGURE 14 Additional SHCV permitting fees being levied. FIGURE 15 Operational details of SHCV permitting. The differences between jurisdictions in terms of the SHCV single-trip permitting fees levied are significant, rang- ing from a flat fee of $10 regardless of the loads involved and the distance traveled to pavement damage-distance-based fees being added to the pavement and bridge analysis fees. Figure 14 shows that 26 of the 32 agencies that responded to these questions (81%) do not collect additional permit fees to cover potential damage to pavement embankments, shoulders, and utilities from SHCVs. Figure 15 shows the distribution of responses from 37 agen- cies on some of their operational practices in handling SHCV permits. • More than half of those that responded have implemented electronic SHCV permit processing systems. • The large majority of those that responded allow wide multi-lane vehicle movements. • Twenty-five percent of the agencies that responded restrict vehicle movements during spring thaw. • Twenty-two percent of the agencies that responded allow multiple trips with one permit. • Fifty-six percent of the agencies that responded coordi- nate their permit provisions with those of neighboring jurisdictions. As pointed out in the literature review, only some of the WASHTO-affiliated states have estab- lished homogenized cross-border heavy vehicle permit- ting standards. FIGURE 12 Actions taken if analysis shows risk of damage to pavement/subgrade.

25 FIGURE 17 Maximum SHCV GVW ever permitted. FIGURE 16 Number of SHCV permits issued annually (2013). shows that several jurisdictions have a SHCV GVW threshold as low as 120 kips). Finally, Figure 17 reveals the distribution of the largest GVW ever permitted in the 46 jurisdictions that responded to this question. The most frequent extreme GVW was under 1,000 kips (41% of the responding jurisdictions), while a few (i.e., 11% of the responding jurisdictions) indi- cated that they have permitted vehicles with a GVW of more than 2,000 kips. NUMBER OF SUPERHEAVY COMMERCIAL VEHICLE PERMITS AND TYPE ISSUED The number of SHCV permits issued annually varies signifi- cantly between jurisdictions. Figure 16 shows that the major- ity of states and provinces issue fewer than 1,000 such permits each year. Several jurisdictions reported a very large number of such permits (e.g., more than 10,000 permits per year) prob- ably as a result of the way they define an SHCV (i.e., Figure 5