Most of the road construction projects in Tanzania had undergone many variation orders, which increased client expenditures beyond the planned budget. Occasionally, disagreements and excessive postponements occurred. Variation order implies alterations in the margin of task scheduling, blueprint, or agreement files in the construction industry, leading to the postponement of projects and additional payments. Therefore, it is essential to manage the variation orders [1]. Matimbe and Lema discovered significant variations in road project costs beyond the original contract sums in a study assessing the cost and time performance of integrated road projects (IRP) in Tanzania [2]. According to the survey, 95% of the sampled projects experienced cost variations ranging from 19 to 216% of the original contract sum, and 70% experienced time variations ranging from 5 to 733% of the initial completion time. Kimambo also stated that the actual project costs for many initial integrated road projects (IRP) were higher than the original estimates [3]. The local components for most civil work contracts were typically more expensive (up to 30% higher) due to changes in exchange rates. Therefore, it is essential to control the order of variation. Several analyses have been conducted to determine the origins of variation orders in road construction projects. A key reason necessitating a variation order is the preference or flavor for a better-completed result that differs from the quality initially agreed upon by the owner in a specific contractual agreement.

Furthermore, owing to consultants, weather, and varying site conditions, changes to an initial design may be required [4]. Burati et al. investigated nine key engineering projects with expense-related deviations to encounter obligations [5]; the authors discovered that character variation is described as 12.4% of the agreed rates in the entire nine projects. Ndihokubwayo and Haupt found that 63% of site instructions were used as additional work and recommended that the design team be more careful at the preliminary stage to avoid unnecessary alteration of results [6]. Moreover, Charoenngam et al. advised that stakeholders should have good communication in the work environment and that capacity building should be provided to the design team because standard construction technology is changing [7]. Likewise, Chan and Yeong suggested that excellent document keeping, appropriate harmonization, and interaction between professionals remain suitable for intolerance of variation order administration [8].

This study investigated the possible causes of variation orders in road construction projects in Tanzania, especially TARURA and TANROADS, which are agencies dealing with the construction and maintenance of roads in Tanzania. The data were collected from four actual projects conducted in Tanzania and 92 respondents working with one of Tanzania's road agencies.

Variation orders arise from various sources, of which some are foreseeable. Many researchers have identified multiple causes for a variation order. Pourrostam and Ismail focused on investigating the causes of variation orders in roadway construction projects and identifying their effects on such projects in southern Iran [9]. Their results showed a low correlation between owners and contractors. Conversely, it showed a good correlation between the employer and contractors, with 97% agreement. It was concluded that employer changes in plans or scope, errors and omissions in design, differing site conditions, and contractors' financial difficulties were some of the critical factors causing variation orders in roadway construction projects.

Halwatura and Ranasinghe also studied road construction projects in Sri Lanka [10]. According to the questionnaire survey, poor estimation was the primary cause of variation order, followed by unexpected site conditions, political pressure during the construction stage, inadequate investigation, and client-initiated variations. The ranking was verified through a case study analysis. Multiple case studies have been conducted by Wu et al. to identify the causes of changes in highway projects in Taiwan [11]. The findings showed that differences in engineering properties among embankments, roads, viaducts, and tunnels create differences in the importance of investigating and managing geological concerns. A site survey was developed in the feasibility analysis and planning design stages for similar future projects.

Sunday examined the impact of variations in construction projects [12]. Variation orders are the most disruptive and unpleasant events of projects because of their implications for the cost and completion date of the project. Msallam et al. focused on the causes of variation in highway projects in Jordan [13]. According to the results, the ten important causes were the change in schedule, ambiguous design details, change of plan or scope, a conflict between contract documents, lack of coordination, safety considerations, client financial problems, change in design by consultants, socio-cultural factors, and changes in government regulations. The analysis revealed that the tasks handled by the consultants were more prone to variation orders than those handled by in-house professionals. The consultants' reasons were unclear drawings, design discrepancies, and conflicts between contract documents.

Additionally, the owners' most contributing causes of variation orders were changes in scope, slow decision processes, and insufficient project shortages. Contractors' reasons included lack of skilled labor, different site conditions, and contractors' desired profitability. The following are the causes of the variation order based on the reviewed literature (Table 1).

Data were collected through a desk study and a questionnaire survey. According to Kothari, a research methodology is an approach to solving a research problem analytically [14]. Various phases can be examined using research methodologies by studying their research problems and reasoning. Desk research refers to secondary data collected without fieldwork. A desk study was conducted on selected road construction projects to identify the causes of a variation order. Data were obtained from project disbursement diplomas and regular development statements to provide information on the stated problem, which aids in comprehending the correlation between the hypotheses and fundamental habits in construction projects. All projects discussed in the four case studies used the design-bid-build delivery technique, in which the client hires a design consultant and then chooses a contractor through a tendering process.

A series of questionnaires were distributed to various respondents to collect data by one of the authors (Roziana Saki). The project management team, consultants, and contractors were also led. It is divided into three sections. The first section included respondents' personal information such as their name, agency name, address, education level, and experience with road construction projects. Furthermore, the second section included questions regarding the causes of the variation order in the road construction field. Finally, the third section focuses on the preventive measures that should be taken to eliminate variation orders. A total of 120 questionnaires were sent electronically in a Google survey (70 from TANRODS and TARURA and 50 from contractors and consultants). The questionnaires were mailed between August 4 and September 2, 2021, and respondents were requested to respond within 28 days.

Results obtained after calculation were ranked as shown in (Table 3). The results reveal that the most significant circumstances causing variation orders are financial problems, weather conditions, differing site conditions, changes in design, poor scheduling, lack of coordination, delay in approval, unavailability of equipment, and lack of communication.

The findings of the desk study revealed 19 causes of a variation order in answering the primary aim. It was blended to 13 from most of the minor repetitive causes of variation orders to be used in the questionnaire for the verification and validation process to evaluate their degree of importance. However, all 13 causes were previously identified within the field of variables in the literature review. The document study summarizes the causes of variation in order from the four project contract documents, as presented in (Table 4).

Based on the data analyzed using the RII method, the financial problem was ranked according to the overall respondents as the first position with RII = 0.7540, which seriously impacts the project and may cause deferral completion. This result was also aligned with Ssegawa et al. (2002), who observed that the client and architect initiated most of the variations due to financial reasons, design, and drawing changes. Weather conditions (RII = 0.6966) were ranked as the second most important cause of variation in Tanzania. It is supported by Ismail et al. (2012), Wu et al. (2015), and Msallam et al. (2015). Differing site conditions were ranked as the third cause with RII=0.6598, change in design as the fourth cause of variation order in a road construction project in Tanzania with an RII of 0.6575, and poor scheduling as the fifth cause of variation with an RII of 0.6506. Changes in government regulations (RI=0.4575) and economic conditions (RI=0.4943) were the minimum-ranked causes of variation orders in road construction projects in Tanzania.

Based on the questionnaire findings, the respondents' proposed recommendations were that all involved parties should plan properly before work starts on site. The purpose was to assist in reducing the occurrence of variations during the construction phase, where the impact of variations can be severe on the project. Detailed site investigations, including detailed soil investigations, and considering it during the tendering stage were also suggested because the design and construction of the road project approach vary due to differences in site conditions. The third recommendation was for consultants to ensure that the design/specifications fall within the approved budget to avoid unnecessary variations. The fourth was to spend adequate time in the pretender planning phase, and the fifth was to obtain accurate information and research regarding procurement procedures, materials, and plants.

This study focuses on weighing the key causes of variation orders in road construction projects in Tanzania by distributing questionnaires among TANROADS and TARURA workers, contractors, and consulting firms. A typical index analysis of the collected information through a survey revealed the top ten causes of variation orders in road construction projects in Tanzania: financial problems, weather conditions, differing site conditions, changes in design, poor scheduling, lack of coordination, delay in approval, unavailability of equipment, lack of communication, and schedule.

Suggestions to minimize variation order incidence were stated as follows:

1. All participating partners must prepare sufficiently before the site commencement. To avoid conflicts, other groups such as water, electricity, and communication should be involved during the design stage.

2. All parties must perform thorough site analysis and geotechnical studies and scrutinize at the bidding stage.

3. Consultants must ensure the blueprints/specifications plunge in authorized fund allocation. Before entering the tender, both parts should be financially prepared to avoid variation in order.

4. Devote sufficient time in the devising stage. Before filling in the bidding document and estimating, contractors must conduct an effective site visit to see all obstacles and consider them in the bid.

5. Investigate and obtain accurate data concerning procurement transactions, materials, and plants. If possible, contractors are advised to obtain the entire amount of specific material to avoid a shortage of material at the site.